code: def serialize(ms, version=_default_version, properties=True,
                pretty_print=False, color=False):
      
      delim = '\n' if pretty_print else _default_mrs_delim
      output = delim.join(
          _serialize_mrs(m, properties=properties,
                         version=version, pretty_print=pretty_print)
          for m in ms
      )
      if color:
          output = highlight(output)
      return output
docs: Serialize an MRS structure into a SimpleMRS string.