code: def physical_pin(self, function):
          
          result = self.physical_pins(function)
          if len(result) > 1:
              raise PinMultiplePins('multiple pins can be used for %s' % function)
          elif result:
              return result.pop()
          else:
              raise PinNoPins('no pins can be used for %s' % function)
docs: Return the physical pin supporting the specified *function*. If no pins
          support the desired *function*, this function raises :exc:`PinNoPins`.
          If multiple pins support the desired *function*, :exc:`PinMultiplePins`
          will be raised (use :func:`physical_pins` if you expect multiple pins
          in the result, such as for electrical ground).
  
          :param str function:
              The pin function you wish to search for. Usually this is something
              like "GPIO9" for Broadcom GPIO pin 9.