message: Improve documentation for TextLineDataset.
  This adds a longer description and includes an example used for TextLineDataset (https://www.tensorflow.org/api_docs/python/tf/data/TextLineDataset)
diff: @@ -141,7 +141,39 @@ class _TextLineDataset(dataset_ops.DatasetSource):
  @tf_export("data.TextLineDataset", v1=[])
  class TextLineDatasetV2(dataset_ops.DatasetSource):
  - """A `Dataset` comprising lines from one or more text files."""
  + r"""Creates a `Dataset` comprising lines from one or more text files.
  +
  + The `tf.data.TextLineDataset` loads text from text files and creates a dataset
  + where each line of the files becomes an element of the dataset.
  +
  + For example, suppose we have 2 files "text_lines0.txt" and "text_lines1.txt"
  + with the following lines:
  +
  + >>> with open('/tmp/text_lines0.txt', 'w') as f:
  + ... f.write('the cow\n')
  + ... f.write('jumped over\n')
  + ... f.write('the moon\n')
  + >>> with open('/tmp/text_lines1.txt', 'w') as f:
  + ... f.write('jack and jill\n')
  + ... f.write('went up\n')
  + ... f.write('the hill\n')
  +
  + We can construct a TextLineDataset from them as follows:
  +
  + >>> dataset = tf.data.TextLineDataset(['/tmp/text_lines0.txt',
  + ... '/tmp/text_lines1.txt'])
  +
  + The elements of the dataset are expected to be:
  +
  + >>> for element in dataset.as_numpy_iterator():
  + ... print(element)
  + b'the cow'
  + b'jumped over'
  + b'the moon'
  + b'jack and jill'
  + b'went up'
  + b'the hill'
  + """
  def __init__(self,
  filenames,
  