layers.py 文件源码

def build(self, input_shape):
        assert len(input_shape) >= 3
        self.input_spec = [InputSpec(shape=input_shape)]
        if K._BACKEND == 'tensorflow':
            if not input_shape[1]:
                raise Exception('When using TensorFlow, you should define '
                                'explicitly the number of timesteps of '
                                'your sequences.\n'
                                'If your first layer is an Embedding, '
                                'make sure to pass it an "input_length" '
                                'argument. Otherwise, make sure '
                                'the first layer has '
                                'an "input_shape" or "batch_input_shape" '
                                'argument, including the time axis.')
        child_input_shape = (input_shape[0],) + input_shape[self.first_n:]
        if not self.layer.built:
            self.layer.build(child_input_shape)
            self.layer.built = True
        super(NTimeDistributed, self).build()