def get_dir_from_zipfile(zip_file, fallback=None):
    """Return the name of the root folder in a zip file.

    :param zip_file: a :class:`zipfile.ZipFile` instance.
    :param fallback: if `None`, the name of the zip file is used. This is
        returned if the zip file contains more than one top-level directory,
        or none at all.
    """
    fallback = fallback or zip_file.filename
    directories = [name for name in zip_file.namelist() if name.endswith("/")
                   and len(PurePath(name).parts) == 1]
    return fallback if len(directories) > 1 else directories[0]
def test_ccode_user_functions():
    x = symbols('x', integer=False)
    n = symbols('n', integer=True)
    custom_functions = {
        "ceiling": "ceil",
        "Abs": [(lambda x: not x.is_integer, "fabs"), (lambda x: x.is_integer, "abs")],
    }
    assert ccode(ceiling(x), user_functions=custom_functions) == "ceil(x)"
    assert ccode(Abs(x), user_functions=custom_functions) == "fabs(x)"
    assert ccode(Abs(n), user_functions=custom_functions) == "abs(n)"