def exists(list_elements, check_function):
    """exists
    Check whether at least an element x of l is True for f(x)
    :param list_elements: A list of elements to test
    :param check_function: The checking function (takes one parameter and  \
    return a boolean)
    """
    for element in list_elements:
        if check_function(element):
            return True
    return False