The channel dimension of the inputs should be defined. Found `None`

Hello I'm trying to use SegNet in my project with tensorflow, for educational purpose. And I'm surely following someone else's code on GitHub:

conv_14 = Conv2D(512, (kernel, kernel), padding=same)(unpool_1)

But it is giving me something like:

The channel dimension of the inputs should be defined. Found `None`.

How can resolve this? I checked, i've passed all the necessary params to it.

Unpooling instance is created somewhat like this:

pool_5, mask_5 = MaxPoolingWithArgmax2D(pool_size)(conv_13)
print(Build enceder done..)

# decoder

unpool_1 = MaxUnpooling2D(pool_size)([pool_5, mask_5])

And when I tried a log in unpool_1 with simple print, it gave me:

KerasTensor(type_spec=TensorSpec(shape=(None, None, None, None), dtype=tf.float32, name=None), name='max_unpooling2d_3/max_unpooling2d_3/ScatterNd:0', description=created by layer 'max_unpooling2d_3')

And un-pooling class looks like this:

class MaxUnpooling2D(Layer):
    def __init__(self, size=(2, 2), **kwargs):
        super(MaxUnpooling2D, self).__init__(**kwargs)
        self.size = size

    def call(self, inputs, output_shape=None):
        updates, mask = inputs[0], inputs[1]
        with K.tf.variable_scope(self.name):
            mask = K.cast(mask, int32)
            input_shape = K.tf.shape(updates, out_type=int32)
            #  calculation new shape
            if output_shape is None:
                output_shape = (
                    input_shape[0],
                    input_shape[1] * self.size[0],
                    input_shape[2] * self.size[1],
                    input_shape[3],
                )
            self.output_shape1 = output_shape

            # calculation indices for batch, height, width and feature maps
            one_like_mask = K.ones_like(mask, dtype=int32)
            batch_shape = K.concatenate([[input_shape[0]], [1], [1], [1]], axis=0)
            batch_range = K.reshape(
                K.tf.range(output_shape[0], dtype=int32), shape=batch_shape
            )
            b = one_like_mask * batch_range
            y = mask // (output_shape[2] * output_shape[3])
            x = (mask // output_shape[3]) % output_shape[2]
            feature_range = K.tf.range(output_shape[3], dtype=int32)
            f = one_like_mask * feature_range

            # transpose indices  reshape update values to one dimension
            updates_size = K.tf.size(updates)
            indices = K.transpose(K.reshape(K.stack([b, y, x, f]), [4, updates_size]))
            values = K.reshape(updates, [updates_size])
            ret = K.tf.scatter_nd(indices, values, output_shape)
            return ret

Reference:

• https://github.com/ykamikawa/tf-keras-SegNet/blob/master/model.py
• https://github.com/ykamikawa/tf-keras-SegNet/blob/master/layers.py

Traceback looks like this:

ValueError                                Traceback (most recent call last)
/tmp/ipykernel_36/2900577033.py in module
    212 
    213 
-- 214 segnet = SegNet(input_shape=(128, 128, 3), n_labels=2)

/tmp/ipykernel_36/2900577033.py in SegNet(input_shape, n_labels, kernel, pool_size, output_mode)
    148     unpool_1 = MaxUnpooling2D(pool_size)([pool_5, mask_5])
    149 
-- 150     conv_14 = Conv2D(512, (kernel, kernel), padding=same)(unpool_1)
    151     conv_14 = BatchNormalization()(conv_14)
    152     conv_14 = Activation(relu)(conv_14)

/opt/conda/lib/python3.7/site-packages/keras/engine/base_layer.py in __call__(self, *args, **kwargs)
    975     if _in_functional_construction_mode(self, inputs, args, kwargs, input_list):
    976       return self._functional_construction_call(inputs, args, kwargs,
-- 977                                                 input_list)
    978 
    979     # Maintains info about the `Layer.call` stack.

/opt/conda/lib/python3.7/site-packages/keras/engine/base_layer.py in _functional_construction_call(self, inputs, args, kwargs, input_list)
   1113       # Check input assumptions set after layer building, e.g. input shape.
   1114       outputs = self._keras_tensor_symbolic_call(
- 1115           inputs, input_masks, args, kwargs)
   1116 
   1117       if outputs is None:

/opt/conda/lib/python3.7/site-packages/keras/engine/base_layer.py in _keras_tensor_symbolic_call(self, inputs, input_masks, args, kwargs)
    846       return tf.nest.map_structure(keras_tensor.KerasTensor, output_signature)
    847     else:
-- 848       return self._infer_output_signature(inputs, args, kwargs, input_masks)
    849 
    850   def _infer_output_signature(self, inputs, args, kwargs, input_masks):

/opt/conda/lib/python3.7/site-packages/keras/engine/base_layer.py in _infer_output_signature(self, inputs, args, kwargs, input_masks)
    884           # overridden).
    885           # TODO(kaftan): do we maybe_build here, or have we already done it?
-- 886           self._maybe_build(inputs)
    887           inputs = self._maybe_cast_inputs(inputs)
    888           outputs = call_fn(inputs, *args, **kwargs)

/opt/conda/lib/python3.7/site-packages/keras/engine/base_layer.py in _maybe_build(self, inputs)
   2657         # operations.
   2658         with tf_utils.maybe_init_scope(self):
- 2659           self.build(input_shapes)  # pylint:disable=not-callable
   2660       # We must set also ensure that the layer is marked as built, and the build
   2661       # shape is stored since user defined build functions may not be calling

/opt/conda/lib/python3.7/site-packages/keras/layers/convolutional.py in build(self, input_shape)
    185   def build(self, input_shape):
    186     input_shape = tf.TensorShape(input_shape)
-- 187     input_channel = self._get_input_channel(input_shape)
    188     if input_channel % self.groups != 0:
    189       raise ValueError(

/opt/conda/lib/python3.7/site-packages/keras/layers/convolutional.py in _get_input_channel(self, input_shape)
    364     channel_axis = self._get_channel_axis()
    365     if input_shape.dims[channel_axis].value is None:
-- 366       raise ValueError('The channel dimension of the inputs '
    367                        'should be defined. Found `None`.')
    368     return int(input_shape[channel_axis])

ValueError: The channel dimension of the inputs should be defined. Found `None`.
```