code: def __decodeModifier(self, keyCode):
          
          keyName = self.lookup_string(keyCode, False, False, False)
          if keyName in MODIFIERS:
              return keyName
  
          return None
docs: Checks if the given keyCode is a modifier key. If it is, returns the modifier name
          constant as defined in the iomediator module. If not, returns C{None}