keras/src/layers/convolutional/base_depthwise_conv.py/BaseDepthwiseConv/_get_input_channel
class BaseDepthwiseConv:    def _get_input_channel(self, input_shape):
        if self.data_format == "channels_last":
            input_channel = input_shape[-1]
        else:
            input_channel = input_shape[1]
        return input_channel