code: def unregister(self, uuid):
          
          schema = self._schbyuuid.pop(uuid)
  
          # clean schemas by name
          self._schbyname[schema.name].remove(schema)
          if not self._schbyname[schema.name]:
              del self._schbyname[schema.name]
docs: Unregister a schema registered with input uuid.
  
          :raises: KeyError if uuid is not already registered.