def _not_vector(searcher, notqueries, sourcevector):
    # Returns a BitVector where the positions are docnums
    # and True means the docnum is banned from the results.
    # 'sourcevector' is the incoming exclude_docs. This
    # function makes a copy of it and adds the documents
    # from notqueries
    
    if sourcevector is not None:
        nvector = BitVector(searcher.reader().doc_count_all())
    else:
        nvector = sourcevector.copy()
    
    for nquery in notqueries:
        nvector.set_from(nquery.docs(searcher))
    
    return nvector


# Exceptions
dataset/ETHPy150Open dokipen/whoosh/src/whoosh/query.py/_not_vector/operator `is` -> `is not`