old_contents: from tqdm import tqdm
  
  from .data_pack import DataPack
  from matchzoo import processor_units
  
  
  def build_unit_from_data_pack(
      unit: processor_units.StatefulProcessorUnit,
      data_pack: DataPack, flatten: bool = True,
      verbose: int = 1
  ) -> processor_units.StatefulProcessorUnit:
      """
      Build a :class:`StatefulProcessorUnit` from a :class:`DataPack` object.
  
      :param unit: :class:`StatefulProcessorUnit` object to be built.
      :param data_pack: The input :class:`DataPack` object.
      :param flatten: Flatten the datapack or not. `True` to organize the
          :class:`DataPack` text as a list, and `False` to organize
          :class:`DataPack` text as a list of list.
      :param verbose: Verbosity.
      :return: A built :class:`StatefulProcessorUnit` object.
  
      """
      corpus = []
      if flatten:
          data_pack.apply_on_text(corpus.extend, verbose=verbose)
      else:
          data_pack.apply_on_text(corpus.append, verbose=verbose)
      if verbose:
          description = 'Building ' + unit.__class__.__name__ + \
                        ' from a datapack.'
          corpus = tqdm(corpus, desc=description)
      unit.fit(corpus)
      return unit
  
new_contents: """Build unit from data pack."""
  
  from tqdm import tqdm
  
  from matchzoo import processor_units
  from .data_pack import DataPack
  
  
  def build_unit_from_data_pack(
      unit: processor_units.StatefulProcessorUnit,
      data_pack: DataPack, flatten: bool = True,
      verbose: int = 1
  ) -> processor_units.StatefulProcessorUnit:
      """
      Build a :class:`StatefulProcessorUnit` from a :class:`DataPack` object.
  
      :param unit: :class:`StatefulProcessorUnit` object to be built.
      :param data_pack: The input :class:`DataPack` object.
      :param flatten: Flatten the datapack or not. `True` to organize the
          :class:`DataPack` text as a list, and `False` to organize
          :class:`DataPack` text as a list of list.
      :param verbose: Verbosity.
      :return: A built :class:`StatefulProcessorUnit` object.
  
      """
      corpus = []
      if flatten:
          data_pack.apply_on_text(corpus.extend, verbose=verbose)
      else:
          data_pack.apply_on_text(corpus.append, verbose=verbose)
      if verbose:
          description = 'Building ' + unit.__class__.__name__ + \
                        ' from a datapack.'
          corpus = tqdm(corpus, desc=description)
      unit.fit(corpus)
      return unit
  
subject: Update docs for build unit.