code: def _parse_protocol_psutil(self, conn):
          
          protocol = self.PSUTIL_TYPE_MAPPING.get(conn.type, '')
          family = self.PSUTIL_FAMILY_MAPPING.get(conn.family, '')
          return '{}{}'.format(protocol, family)
docs: Returns a string describing the protocol for the given connection
          in the form `tcp4`, 'udp4` as in `self.cx_state_gauge`