code: def wwpn_free(self, wwpn):
          
          wwpn_int = int(wwpn[-4:], 16)
          self._wwpn_pool.free(wwpn_int)
docs: Free a WWPN allocated with :meth:`wwpn_alloc`.
  
          The WWPN must be allocated.
  
          Parameters:
            WWPN (string): The WWPN as 16 hexadecimal digits.
  
          Raises:
            ValueError: WWPN not in pool range or not currently
              allocated.