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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 extract(dump_files, extractors=ALL_EXTRACTORS):
 """ Extracts cites from a set of `dump_files`. :Parameters: dump_files : str | `file` A set of files MediaWiki XML dump files (expects: pages-meta-history) extractors : `list`(`extractor`) A list of extractors to apply to the text :Returns: `iterable` -- a generator of extracted cites """

    # Dump processor function
    def process_dump(dump, path):
        for page in dump:
            if page.namespace != 0: continue
            else:
                for cite in extract_cite_history(page, extractors):
                    yield cite

    # Map call
    return mwxml.map(process_dump, dump_files)