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_Indexed():
    from sympy.tensor import IndexedBase, Idx
    from sympy import symbols
    n, m, o = symbols('n m o', integer=True)
    i, j, k = Idx('i', n), Idx('j', m), Idx('k', o)
    p = CCodePrinter()
    p._not_c = set()

    x = IndexedBase('x')[j]
    assert p._print_Indexed(x) == 'x[j]'
    A = IndexedBase('A')[i, j]
    assert p._print_Indexed(A) == 'A[%s]' % (m*i+j)
    B = IndexedBase('B')[i, j, k]
    assert p._print_Indexed(B) == 'B[%s]' % (i*o*m+j*o+k)

    assert p._not_c == set()