from typing import Dict
from typing import List


def allowed_external_connections(csp_config: Dict) -> List[str]:
    """ Returns a list of ``https://`` sources from `csp_config`. """
    connections = []
    for _, sources in csp_config.items():
        for source in sources:
            if source.startswith("https://"):
                connections.append(source)
    return list(dict.fromkeys(connections))