class Image(Directive):

    align_h_values = ('left', 'center', 'right')
    align_v_values = ('top', 'middle', 'bottom')
    align_values = align_v_values + align_h_values
    loading_values = ('embed', 'link', 'lazy')

    def align(argument):
        # This is not callable as `self.align()`.  We cannot make it a
        # staticmethod because we're saving an unbound method in
        # option_spec below.
        return directives.choice(argument, Image.align_values)

    def loading(argument):
        # This is not callable as `self.loading()` (see above).
        return directives.choice(argument, Image.loading_values)

    required_arguments = 1
    optional_arguments = 0
    final_argument_whitespace = True
    option_spec = {'alt': directives.unchanged,
                   'height': directives.length_or_unitless,
                   'width': directives.length_or_percentage_or_unitless,
                   'scale': directives.percentage,
                   'align': align,
                   'target': directives.unchanged_required,
                   'loading': loading,
                   'class': directives.class_option,
                   'name': directives.unchanged}