code: def sibling(self, name: InstanceName) -> "ObjectMember":
          
          ssn = self.parinst._member_schema_node(name)
          try:
              sibs = self.siblings.copy()
              newval = sibs.pop(name)
              sibs[self.name] = self.value
              return ObjectMember(name, sibs, newval, self.parinst,
                                  ssn, self.timestamp)
          except KeyError:
              raise NonexistentInstance(self.json_pointer(),
                                        f"member '{name}'") from None
docs: Return an instance node corresponding to a sibling member.
  
          Args:
              name: Instance name of the sibling member.
  
          Raises:
              NonexistentSchemaNode: If member `name` is not permitted by the
                  schema.
              NonexistentInstance: If sibling member `name` doesn't exist.