def _init_mutable_colormap():
 greys = color_palette('Greys', 256)
 cmap = LinearSegmentedColormap.from_list('interactive', greys)
 cmap._init()
 cmap._set_extremes()
 return cmap

def _init_mutable_colormap ( ) : greys = color_palette ( 'Greys' , 256 ) cmap = LinearSegmentedColormap . from_list ( 'interactive' , greys ) cmap . _init ( ) cmap . _set_extremes ( ) return cmap
create a matplotlib colormap that will be updated by the widgets .