def read_sources(sf):
    """
    Read the sources.txt file that has source of ORF call, ORF id
    :param sf: sources.txt file
    :return: dict of ORF/source
    """

    s = {}
    with open(sf, 'r') as f:
        for l in f:
            p = l.strip().split("\t")
            s[p[0]] = p[1]
    return s