code: def bind_addr(self, value):
          
          if isinstance(value, tuple) and value[0] in ('', None):
              # Despite the socket module docs, using '' does not
              # allow AI_PASSIVE to work. Passing None instead
              # returns '0.0.0.0' like we want. In other words:
              #     host    AI_PASSIVE     result
              #      ''         Y         192.168.x.y
              #      ''         N         192.168.x.y
              #     None        Y         0.0.0.0
              #     None        N         127.0.0.1
              # But since you can get the same effect with an explicit
              # '0.0.0.0', we deny both the empty string and None as values.
              raise ValueError(
                  "Host values of '' or None are not allowed. "
                  "Use '0.0.0.0' (IPv4) or '::' (IPv6) instead "
                  'to listen on all active interfaces.',
              )
          self._bind_addr = value
docs: Set the interface on which to listen for connections.