old_contents: """Module with helper functions for comparing datasets."""
  
  def diff_identifiers(a, b):
      """Return list of tuples where identifiers in datasets differ.
  
      Tuple structure:
      (identifier, present in a, present in b)
  
      :param a: first :class:`dtoolcore.DataSet`
      :param b: second :class:`dtoolcore.DataSet`
      :returns: list of tuples where identifiers in datasets differ
      """
  
      a_ids = set(a.identifiers)
      b_ids = set(b.identifiers)
  
      difference = []
  
      for i in a_ids.difference(b_ids):
          difference.append((i, True, False))
      for i in b_ids.difference(a_ids):
          difference.append((i, False, True))
  
      return difference
  
  
  def diff_sizes(a, b):
      """Return list of tuples where sizes differ.
  
      Tuple structure:
      (identifier, size in a, size in b)
  
      Assumes list of identifiers in a and b are identical.
  
      :param a: first :class:`dtoolcore.DataSet`
      :param b: second :class:`dtoolcore.DataSet`
      :returns: list of tuples for all items with different sizes
      """
      difference = []
  
      for i in a.identifiers:
          a_size = a.item_properties(i)["size_in_bytes"]
          b_size = b.item_properties(i)["size_in_bytes"]
          if a_size != b_size:
              difference.append((i, a_size, b_size))
  
      return difference
  
  
  def diff_content(a, reference):
      """Return list of tuples where content differ.
  
      Tuple structure:
      (identifier, hash in a, hash in reference)
  
      Assumes list of identifiers in a and b are identical.
  
      Storage broker of reference used to generate hash for files in a.
  
      :param a: first :class:`dtoolcore.DataSet`
      :param b: second :class:`dtoolcore.DataSet`
      :returns: list of tuples for all items with different content
      """
      difference = []
  
      for i in a.identifiers:
          fpath = a.item_content_abspath(i)
          calc_hash = reference._storage_broker.hasher(fpath)
          ref_hash = reference.item_properties(i)["hash"]
          if calc_hash != ref_hash:
              info = (i, calc_hash, ref_hash)
              difference.append(info)
  
      return difference
  
new_contents: """Module with helper functions for comparing datasets."""
  
  
  def diff_identifiers(a, b):
      """Return list of tuples where identifiers in datasets differ.
  
      Tuple structure:
      (identifier, present in a, present in b)
  
      :param a: first :class:`dtoolcore.DataSet`
      :param b: second :class:`dtoolcore.DataSet`
      :returns: list of tuples where identifiers in datasets differ
      """
  
      a_ids = set(a.identifiers)
      b_ids = set(b.identifiers)
  
      difference = []
  
      for i in a_ids.difference(b_ids):
          difference.append((i, True, False))
      for i in b_ids.difference(a_ids):
          difference.append((i, False, True))
  
      return difference
  
  
  def diff_sizes(a, b):
      """Return list of tuples where sizes differ.
  
      Tuple structure:
      (identifier, size in a, size in b)
  
      Assumes list of identifiers in a and b are identical.
  
      :param a: first :class:`dtoolcore.DataSet`
      :param b: second :class:`dtoolcore.DataSet`
      :returns: list of tuples for all items with different sizes
      """
      difference = []
  
      for i in a.identifiers:
          a_size = a.item_properties(i)["size_in_bytes"]
          b_size = b.item_properties(i)["size_in_bytes"]
          if a_size != b_size:
              difference.append((i, a_size, b_size))
  
      return difference
  
  
  def diff_content(a, reference):
      """Return list of tuples where content differ.
  
      Tuple structure:
      (identifier, hash in a, hash in reference)
  
      Assumes list of identifiers in a and b are identical.
  
      Storage broker of reference used to generate hash for files in a.
  
      :param a: first :class:`dtoolcore.DataSet`
      :param b: second :class:`dtoolcore.DataSet`
      :returns: list of tuples for all items with different content
      """
      difference = []
  
      for i in a.identifiers:
          fpath = a.item_content_abspath(i)
          calc_hash = reference._storage_broker.hasher(fpath)
          ref_hash = reference.item_properties(i)["hash"]
          if calc_hash != ref_hash:
              info = (i, calc_hash, ref_hash)
              difference.append(info)
  
      return difference
  
subject: Fix flake8 issue