Get the method by name and descriptor,
        or create a new one if the requested method does not exists.

        :param name: method name
        :param descriptor: method descriptor, for example `'(I)V'`
        :return: :class:`ExternalMethod`

def get_method(self, name, descriptor):
        """
        Get the method by name and descriptor,
        or create a new one if the requested method does not exists.

        :param name: method name
        :param descriptor: method descriptor, for example `'(I)V'`
        :return: :class:`ExternalMethod`
        """
        key = name + str(descriptor)
        if key not in self.methods:
            self.methods[key] = ExternalMethod(self.name, name, descriptor)

        return self.methods[key]