from typing import Dict
import re


def regex_category_identification(text: str, dict_category: Dict[str, str]) -> str:
    """Use regular expressions to determine a category of a text string.

    :param text: A text string for category identification; the text case is ignored.
    :param dict_category: A dictionary where the keys are possible categories, and the values are regular expression
        patterns that match said category.
    :return: A string of the category from the keys of `dict_category`, or 'unknown' if no matching categories exist.
    """

    # Iterate through `dict_category` in key order, and search for the regular expression pattern in `text`; return the
    # key, i.e. the category, if there is a match
    for k, v in dict_category.items():
        if re.search(v, text, re.IGNORECASE):
            return k

    # If there are no matches with any theme keys in `dict_category`, return 'unknown'
    return "unknown"