code: def access(cls, parent, placeholder):
          
          try:
              return parent.lookup_field_by_placeholder(placeholder)
          except KeyError:
              field_placeholder, name = placeholder.args
              # Find the field whose attribute is being accessed.
              field = parent.lookup_field_by_placeholder(field_placeholder)
              # Instantiate the real FieldAccessor that wraps the attribute.
              accessor = cls(field, name, parent=parent, instantiate=True)
              # Keep this instance alive, and reuse it for future references.
              parent._placeholder_to_field[placeholder] = accessor
              return accessor
docs: Resolve the deferred field attribute access.
  
          :param cls: the FieldAccessor class
          :param parent: owning structure of the field being accessed
          :param placeholder: FieldPlaceholder object which holds our info
          :returns: FieldAccessor instance for that field's attribute