from typing import List
import re


def _find_matching_tags(tag: 'str', lst: 'List[str]'):
    """
    Extract the full list of matches to the regex stored in tag.

    :param tag: A regex to search for
    :type tag: str
    :param lst: A set of tags to search
    :type lst: List[str]

    :return: The matching tags from lst
    :rtype: list[str]
    """
    return [match
            for match in lst
            if re.fullmatch(tag, match)]