code: def dict_to_source(dict):
      '''
      Transform a dict with key 'citation' into a :class:`Source`.
  
      If the argument passed is already a :class:`Source`, this method just
      returns the argument.
      '''
  
      if isinstance(dict, Source):
          return dict
      return Source(
          dict['citation'],
          dict.get('markup')
      f dict_to_source(dict):
      '''
      Transform a dict with key 'citation' into a :class:`Source`.
  
      If the argument passed is already a :class:`Source`, this method just
      returns the argument.
      '''
  
      if isinstance(dict, Source):
          return dict
      return Source(
          dict['citation'],
          dict.get('markup')
      )
docs: Transform a dict with key 'citation' into a :class:`Source`.
  
      If the argument passed is already a :class:`Source`, this method just
      returns the argument.