code: def to_gremlin(self):
          
          self.validate()
  
          local_object_name = self.get_local_object_gremlin_name()
  
          if self.field_name == '@this':
              return local_object_name
  
          if '@' in self.field_name:
              return u'{}[\'{}\']'.format(local_object_name, self.field_name)
          else:
              return u'{}.{}'.format(local_object_name, self.field_name)
docs: Return a unicode object with the Gremlin representation of this expression.