code: def _effective_value(self, attr_name):
          
          directly_applied_value = getattr(
              super(_InheritsDimensions, self), attr_name
          )
          if directly_applied_value is not None:
              return directly_applied_value
          return self._inherited_value(attr_name)
docs: The effective value of *attr_name* on this placeholder shape; its
          directly-applied value if it has one, otherwise the value on the
          layout placeholder it inherits from.