def _index_document(index_list):
    """Helper to generate an index specifying document.

    Takes a list of (key, direction) pairs.
    """
    if isinstance(index_list, abc.Mapping):
        raise TypeError("passing a dict to sort/create_index/hint is not "
                        "allowed - use a list of tuples instead. did you "
                        "mean %r?" % list(iteritems(index_list)))
    elif not isinstance(index_list, (list, tuple)):
        raise TypeError("must use a list of (key, direction) pairs, "
                        "not: " + repr(index_list))
    if not len(index_list):
        raise ValueError("key_or_list must not be the empty list")

    index = SON()
    for (key, value) in index_list:
        if not isinstance(key, string_type):
            raise TypeError("first item in each key pair must be a string")
        if not isinstance(value, (string_type, int, abc.Mapping)):
            raise TypeError("second item in each key pair must be 1, -1, "
                            "'2d', 'geoHaystack', or another valid MongoDB "
                            "index specifier.")
        index[key] = value
    return index
Helper to generate an index specifying document.

    Takes a list of (key, direction) pairs.
    
stackoverflow/venv/lib/python3.6/site-packages/pymongo/helpers.py