code: def get_num_image_channels(module_or_spec, signature=None, input_name=None):
    
    if input_name is None:
      input_name = "images"
    input_info_dict = module_or_spec.get_input_info_dict(signature)
    try:
      shape = input_info_dict[input_name].get_shape()
    except KeyError:
      raise ValueError("Module is missing input '%s' in signature '%s'." %
                       (input_name, signature or "default"))
    try:
      _, _, _, num_channels = shape.as_list()
      if num_channels is None:
        raise ValueError
    except ValueError:
      raise ValueError(
          "Shape of module input is %s, "
          "expected [batch_size, height, width, num_channels] "
          "with known num_channels" % shape)
    return num_channels
docs: Returns expected num_channels dimensions of an image input.
  
    This is for advanced users only who expect to handle modules with
    image inputs that might not have the 3 usual RGB channels.
  
    Args:
      module_or_spec: a Module or ModuleSpec that accepts image inputs.
      signature: a string with the key of the signature in question.
        If None, the default signature is used.
      input_name: a string with the input name for images. If None, the
        conventional input name `images` for the default signature is used.
  
    Returns:
      An integer with the number of input channels to the module.
  
    Raises:
      ValueError: If the channel information is missing or malformed.