[yaml] various inline provider doc fixes

sdks/python/apache_beam/yaml/yaml_combine.py

@@ -94,6 +94,12 @@ class PyJsYamlCombine(beam.PTransform):
 
   See also the documentation on
   [YAML Aggregation](https://beam.apache.org/documentation/sdks/yaml-combine/).
+
+  Args:
+    group_by: The field to aggregate on.
+    combine: The aggregation function to use.
+    language: The language used to define (and execute) the
+      custom callables in `combine`. Defaults to generic.
   """
   def __init__(
       self,

sdks/python/apache_beam/yaml/yaml_mapping.py

@@ -428,19 +428,19 @@ class _StripErrorMetadata(beam.PTransform):
 
   For example, in the following pipeline snippet::
 
-    - name: MyMappingTransform
-      type: MapToFields
-      input: SomeInput
-      config:
-        language: python
-        fields:
-          ...
-        error_handling:
-          output: errors
-
-    - name: RecoverOriginalElements
-      type: StripErrorMetadata
-      input: MyMappingTransform.errors
+      - name: MyMappingTransform
+        type: MapToFields
+        input: SomeInput
+        config:
+          language: python
+          fields:
+            ...
+          error_handling:
+            output: errors
+
+      - name: RecoverOriginalElements
+        type: StripErrorMetadata
+        input: MyMappingTransform.errors
 
   the output of `RecoverOriginalElements` will contain exactly those elements
   from SomeInput that failed to processes (whereas `MyMappingTransform.errors`
@@ -453,6 +453,9 @@ class _StripErrorMetadata(beam.PTransform):
 
   _ERROR_FIELD_NAMES = ('failed_row', 'element', 'record')
 
+  def __init__(self):
+    super().__init__(label=None)
+
   def expand(self, pcoll):
     try:
       existing_fields = {