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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_federation_service(domain, allow_http=False):
 """Retrieve the FEDERATION_SERVER config from a domain's stellar.toml. :param str domain: The domain the .toml file is hosted at. :param bool allow_http: Specifies whether the request should go over plain HTTP vs HTTPS. Note it is recommend that you *always* use HTTPS. :return str: The FEDERATION_SERVER url. """

    st = get_stellar_toml(domain, allow_http)
    if not st:
        return None
    return st.get('FEDERATION_SERVER')