code: def char_in(string, func_name): 
    '''return current char and step if char is in string, where 
     @test: a python function with one argument, which tests on one char and return True or False
            @test must be registered with register_function'''
    function = register_function(func_name, 
                        lambda char: char in string)
    return char_on_predicate(functionf char_in(string, func_name): 
    '''return current char and step if char is in string, where 
     @test: a python function with one argument, which tests on one char and return True or False
            @test must be registered with register_function'''
    function = register_function(func_name, 
                        lambda char: char in string)
    return char_on_predicate(function)
docs: return current char and step if char is in string, where 
     @test: a python function with one argument, which tests on one char and return True or False
            @test must be registered with register_function