docs: def set_url(self, url=None):
          """Sets the url.
  
          :param url: the new copyright
          :type url: ``string``
          :raise: ``InvalidArgument`` -- ``url`` is invalid
          :raise: ``NoAccess`` -- ``Metadata.isReadOnly()`` is ``true``
          :raise: ``NullArgument`` -- ``url`` is ``null``
  
          *compliance: mandatory -- This method must be implemented.*
  
          """
          if url is None:
              raise NullArgument()
          metadata = Metadata(**settings.METADATA['url'])
          if metadata.is_read_only():
              raise NoAccess()
          if self._is_valid_input(url, metadata, array=False):
              self._my_map['url'] = url
          else:
              raise InvalidArgument()