code: def filter_evidence_source(stmts_in, source_apis, policy='one', **kwargs):
      logger.info('Filtering %d statements to evidence source "%s" of: %s...' %
                  (len(stmts_in), policy, ', '.join(source_apis)))
      stmts_out = []
      for st in stmts_in:
          sources = set([ev.source_api for ev in st.evidence])
          if policy == 'one':
              if sources.intersection(source_apis):
                  stmts_out.append(st)
          if policy == 'all':
              if sources.intersection(source_apis) == set(source_apis):
                  stmts_out.append(st)
          if policy == 'none':
              if not sources.intersection(source_apis):
                  stmts_out.append(st)
      logger.info('%d statements after filter...' % len(stmts_out))
      dump_pkl = kwargs.get('save')
      if dump_pkl:
          dump_statements(stmts_out, dump_pkl)
      return stmts_out