code: def instantiate(self):
          
          if self.instance is None:
              self.instance = checked_call(self.cls, self.kwds)
          #endif
          try:
              self.instance.yaml_src = self.yaml_src
          except AttributeError:
              pass
          return self.instance
docs: Instantiate this object with the supplied parameters in `self.kwds`,
          or if already instantiated, return the cached instance.