45_inside-the-token-classification-pipeline-(pytorch).srt

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- 我们来看一下
- Let's have a look

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在 token 分类管线( pipeline )内。
inside the token classification pipeline.

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在有关管线视频中，
In the pipeline video,

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我们学习了不同的应用
we looked at the different applications

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transformers 库支持开箱即用的，
the Transformers library supports out of the box,

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其中之一是 token 分类，
one of them being token classification,

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例如预测句子中的每个单词
for instance predicting for each word in a sentence

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是否对应于一个人，一个组织
whether they correspond to a person, an organization

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或一个位置。
or a location.

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我们甚至可以将相应的 token 组合在一起
We can even group together the tokens corresponding

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到同一个实体，例如所有 token 
to the same entity, for instance all the tokens

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在这里形成了 Sylvain 这个词，或 Hugging 和 Face。
that formed the word Sylvain here, or Hugging and Face.

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 token 分类管线的工作方式相同
The token classification pipeline works the same way

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和我们研究的文本分类的管线
as the text classification pipeline we studied

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在上一个视频中。
in the previous video.

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分为三个步骤。
There are three steps.

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分词化、模型和后处理。
The tokenization, the model, and the postprocessing.

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前两个步骤相同
The first two steps are identical

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到文本分类管线，
to the text classification pipeline,

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除了我们使用 auto (自动) 的 token 分类模型
except we use an auto token classification model

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而不是序列分类。
instead of a sequence classification one.

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我们分词化我们的文本，然后将其提供给模型。
We tokenize our text then feed it to the model.

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而不是为每个可能的标签获取一个数字
Instead of getting one number for each possible label

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对于整个句子，我们得到一个数字
for the whole sentence, we get one number

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对于可能的九个标签中的每一个
for each of the possible nine labels

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对于句子中的每个 token ，此处为 19。
for every token in the sentence, here 19.

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与 transformers 库的所有其他模型一样，
Like all the other models of the transformers library,

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我们的模型输出 logits，
our model outputs logits,

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我们使用 SoftMax 将其转化为预测值。
which we turn into predictions by using a SoftMax.

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我们还获得了每个 token 的预测标签
We also get the predicted label for each token

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通过最大预测，
by taking the maximum prediction,

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因为 SoftMax 函数保留了顺序，
since the SoftMax function preserves the orders,

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我们本可以在 logits 上完成
we could have done it on the logits

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如果我们不需要预测。
if we had no need of the predictions.

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模型配置包含标签映射
The model config contains the label mapping

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在其 id2label 字段中。
in its id2label field.

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使用它，我们可以将每个 token 映射到其相应的标签。
Using it, we can map every token to its corresponding label.

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标签 O 不对应任何实体，
The label, O, correspond to no entity,

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这就是为什么我们没有在结果中看到它
which is why we didn't see it in our results

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在第一张幻灯片中。
in the first slide.

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在标签和概率之上，
On top of the label and the probability,

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这些结果包括开始
those results included the start

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和句末字符。
and end character in the sentence.

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我们需要使用偏移映射
We'll need to use the offset mapping

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分词器得到那些。
of the tokenizer to get those.

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看看下面链接的视频
Look at the video linked below

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如果你还不知道它们。
if you don't know about them already.

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然后，遍历每个 token 
Then, looping through each token

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具有不同于 O 的标签，
that has a label distinct from O,

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我们可以建立我们得到的结果列表
we can build the list of results we got

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用我们的第一条管线。
with our first pipeline.

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最后一步是将 token 组合在一起
The last step is to group together tokens

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对应于同一个实体。
that correspond to the same entity.

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这就是为什么我们为每种类型的实体设置了两个标签，
This is why we had two labels for each type of entity,

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例如，I-PER 和 B-PER。
I-PER and B-PER, for instance.

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它让我们知道一个 token 是否是
It allows us to know if a token is

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在与前一个相同的实体中。
in the same entity as the previous one.

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请注意，有两种标记方式
Note, that there are two ways of labeling used

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用于 token 分类。
for token classification.

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一个，这里是粉红色的，使用 B-PER 标签
One, in pink here, uses the B-PER label

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在每个新实体的开始，
at the beginning of each new entity,

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但另一个，蓝色的，
but the other, in blue,

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只用它来分隔两个相邻的实体
only uses it to separate two adjacent entities

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同类型的。
of the same type.

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在这两种情况下，我们都可以标记一个新实体
In both cases, we can flag a new entity

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每次我们看到一个新标签出现时，
each time we see a new label appearing,

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带有 I 或 B 前缀，
either with the I or B prefix,

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然后将以下所有标记为相同的标记，
then take all the following tokens labeled the same,

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带有 I 标志。
with an I-flag.

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这与偏移映射一起开始
This, coupled with the offset mapping to get the start

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和结束字符允许我们获得文本的跨度
and end characters allows us to get the span of texts

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对于每个实体。
for each entity.

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