import re

    Pattern,

    Union,

Regexp = Union[str, Pattern]

def filter_meta_match(postings: Postings, key: MetaKey, regexp: Regexp) -> Postings:

    for post in postings:

        try:

            if re.search(regexp, post.meta[key]):

                yield post

        except (KeyError, TypeError):

            pass

@pytest.mark.parametrize('key,regexp,expected_indexes', [

    ('entity', '^Smith-', range(5)),

    ('receipt', r'\.pdf$', range(5)),

    ('receipt', 'Receipt', range(3)),

    ('statement', '.', [4]),

    ('metadate', 'foo', ()),

    ('BadKey', '.', ()),

    ('emptykey', '.', ()),

])

def test_filter_meta_match(cc_txn_pair, key, regexp, expected_indexes):

    postings = data.Posting.from_entries(cc_txn_pair)

    actual = filters.filter_meta_match(postings, key, regexp)

    check_filter(actual, cc_txn_pair, expected_indexes)