code: def to_match(self):
          
          self.validate()
  
          mark_name, field_name = self.location.get_location_name()
          validate_safe_string(mark_name)
  
          if field_name is not None:
              raise AssertionError(u'Vertex location has non-None field_name: '
                                   u'{} {}'.format(field_name, self.location))
  
          return mark_name
docs: Return a unicode object with the MATCH representation of this expression.