Add access example to DataFrame docs (#1001) (#1004)

lib/explorer/data_frame.ex

@@ -188,6 +188,12 @@ defmodule Explorer.DataFrame do
       iex> df["class"][3]
       1
 
+  When trying to access a column in the dataframe that does not exist, an `ArgumentError` is raised.
+
+      iex> df =  Explorer.DataFrame.new(a: [1, 2, 3])
+      iex> df["b"]
+      ** (ArgumentError) could not find column name "b". The available columns are: ["a"].
+      If you are attempting to interpolate a value, use ^b.
   """
 
   alias __MODULE__, as: DataFrame

lib/explorer/shared.ex

@@ -265,7 +265,7 @@ defmodule Explorer.Shared do
             List.to_string(
               [
                 "could not find column name \"#{name}\"" | did_you_mean(name, df.names)
-              ] ++ ["\nIf you are attempting to interpolate a value, use ^#{name}.\n"]
+              ] ++ ["\nIf you are attempting to interpolate a value, use ^#{name}."]
             )
     end
   end

test/explorer/series_test.exs

@@ -3471,7 +3471,7 @@ defmodule Explorer.SeriesTest do
       s = Series.from_list([1, 2, 3, 4])
 
       message =
-        "could not find column name \"n\". The available columns are: [\"_\"].\nIf you are attempting to interpolate a value, use ^n.\n"
+        "could not find column name \"n\". The available columns are: [\"_\"].\nIf you are attempting to interpolate a value, use ^n."
 
       assert_raise ArgumentError, message, fn ->
         Series.filter(s, n > 2)
@@ -3521,7 +3521,7 @@ defmodule Explorer.SeriesTest do
       s = Series.from_list([1, 2, 3, 4])
 
       message =
-        "could not find column name \"n\". The available columns are: [\"_\"].\nIf you are attempting to interpolate a value, use ^n.\n"
+        "could not find column name \"n\". The available columns are: [\"_\"].\nIf you are attempting to interpolate a value, use ^n."
 
       assert_raise ArgumentError, message, fn ->
         Series.map(s, n * 2)