human
Solve the following python programming problem given the following code:
def main() : 
    from.traitsui_gradient_editor import make_test_table 
    import sys 
    (table, ctf, otf) = make_test_table (lut = False) 
    def on_color_table_changed() : 
        'If we had a vtk window running, update it here' 
        print ('Update Render Window') 
app = QtGui.QApplication.instance () 
    editor = QGradientEditor (table, <MASK>, colors = ['rgb', 'a', 'h', 's', 'v']) 
    editor.setWindowTitle ('Gradient editor') 
    editor.show () 
    sys.exit (app.exec_ ()) 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is Python program to print ('Update Render Window') 
.
def on_color_table_changed(