Return a specific method by using an index
        :param idx: the index of the method
        :type idx: int

        :rtype: None or an :class:`EncodedMethod` object

def get_method_by_idx(self, idx):
        """
        Return a specific method by using an index
        :param idx: the index of the method
        :type idx: int

        :rtype: None or an :class:`EncodedMethod` object
        """
        if self.__cached_methods_idx is None:
            self.__cached_methods_idx = {}
            for i in self.get_classes():
                for j in i.get_methods():
                    self.__cached_methods_idx[j.get_method_idx()] = j

        try:
            return self.__cached_methods_idx[idx]
        except KeyError:
            return None