Returns a kwarg dict suitable for a ColorScale

def _process_cmap(cmap):
    '''
    Returns a kwarg dict suitable for a ColorScale
    '''
    option = {}
    if isinstance(cmap, str):
        option['scheme'] = cmap
    elif isinstance(cmap, list):
        option['colors'] = cmap
    else:
        raise ValueError('''`cmap` must be a string (name of a color scheme)
                         or a list of colors, but a value of {} was given
                         '''.format(cmap))
    return option