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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 load_sources(filename):
 """ Open a file, read contents, return a list of all the sources in that file. @param filename: @return: list of OutputSource objects """

    catalog = catalogs.table_to_source_list(catalogs.load_table(filename))
    logging.info("read {0} sources from {1}".format(len(catalog), filename))
    return catalog