old_contents: # coding: utf-8
  """Definition of the `Description` class.
  """
  from __future__ import absolute_import
  from __future__ import unicode_literals
  
  import re
  import six
  
  
  class Description(six.text_type):
      """A description with optional cross-references.
      """
  
      _RX_OBO_EXTRACTER = re.compile(r'[\"\'](.*)[\"\']( \[(.+)\])?')
  
      @classmethod
      def from_obo(cls, obo_header):
          match = cls._RX_OBO_EXTRACTER.search(obo_header)
          if match is not None:
              desc, _, xref = match.groups()
          else:
              print(obo_header)
              raise ValueError("not a valid obo definition")
          if xref is not None:
              xref = [x.split(' ')[0] for x in xref.split(', ')]
          return cls(desc, xref)
  
      def __new__(cls, text, xref=None):
          return super(Description, cls).__new__(cls, text)
  
      def __init__(self, text, xref=None):
          self.xref = xref or []
  
      def __repr__(self):
          return "Description('{}', {})".format(self, self.xref)
  
      @property
      def obo(self):
          return 'def: "{}" [{}]'.format(
              self, ', '.join(self.xref)
          )
  
new_contents: # coding: utf-8
  """Definition of the `Description` class.
  """
  from __future__ import absolute_import
  from __future__ import unicode_literals
  
  import re
  import six
  
  
  class Description(six.text_type):
      """A description with optional cross-references.
      """
  
      _RX_OBO_EXTRACTER = re.compile(r'[\"\'](.*)[\"\']( \[(.+)\])?')
  
      @classmethod
      def from_obo(cls, obo_header):
          match = cls._RX_OBO_EXTRACTER.search(obo_header)
          if match is not None:
              desc, _, xref = match.groups()
          else:
              raise ValueError("not a valid obo definition")
          if xref is not None:
              xref = [x.split(' ')[0] for x in xref.split(', ')]
          return cls(desc, xref)
  
      def __new__(cls, text, xref=None):
          return super(Description, cls).__new__(cls, text)
  
      def __init__(self, text, xref=None):
          self.xref = xref or []
  
      def __repr__(self):
          return "Description('{}', {})".format(self, self.xref)
  
      @property
      def obo(self):
          return 'def: "{}" [{}]'.format(
              self, ', '.join(self.xref)
          )
  
subject: Remove stray `print` in `description.py`