def _validate_kwargs(input_dict, compare_dict):
    """
    Function to deal with keyword arguments.

    :param input_dict: matplotlib kwargs dictionary with custom arguments
    :type input_dict: :class: `dict`
    :param compare_dict: matplotlib kwargs of default to use arguments
    :type compare_dict: :class: `dict`
    """
    # Set the default plot kwargs
    for key, val in compare_dict.items():
        # Make sure they aren't already assigned
        if input_dict is None:
            input_dict = compare_dict.copy()
        else:
            if key not in input_dict:
                input_dict[key] = val
    # Return
    return input_dict