registers custom color maps

def register_custom_colormaps():
    """
    registers custom color maps
    """
    if not HAS_MPL:
        return ()
    makemap = LinearSegmentedColormap.from_list
    for name, val in custom_colormap_data.items():
        cm1 = np.array(val).transpose().astype('f8')/256.0
        cm2 = cm1[::-1]
        nam1 = name
        nam2 = '%s_r' % name
        register_cmap(name=nam1, cmap=makemap(nam1, cm1, 256), lut=256)
        register_cmap(name=nam2, cmap=makemap(nam2, cm2, 256), lut=256)

    return ('stdgamma', 'red', 'green', 'blue', 'red_heat', 'green_heat',
            'blue_heat', 'magenta', 'yellow', 'cyan')