code: def get_method_descriptor(self, class_name, method_name, descriptor):
          
          key = class_name + method_name + descriptor
  
          if self.__cache_methods is None:
              self.__cache_methods = {}
              for i in self.get_classes():
                  for j in i.get_methods():
                      self.__cache_methods[j.get_class_name() + j.get_name() +
                                           j.get_descriptor()] = j
  
          return self.__cache_methods.get(key)
docs: Return the specific method
  
          :param class_name: the class name of the method
          :type class_name: string
          :param method_name: the name of the method
          :type method_name: string
          :param descriptor: the descriptor of the method
          :type descriptor: string
  
          :rtype: None or a :class:`EncodedMethod` object