def set_on_event(new_value, traverser):

    if (isinstance(new_value, jstypes.JSLiteral) and
        isinstance(new_value.get_literal_value(traverser), types.StringTypes)):
        warn(traverser.err,
             filename=traverser.filename,
             line=traverser.line,
             column=traverser.position,
             context=traverser.context,
             violation_type="setting_on-event")
Ensure that on* properties are not assigned string values.
dataset/ETHPy150Open mozilla/app-validator/appvalidator/testcases/javascript/instanceproperties.py/set_on_event