index_to_array.py

###########################################
# serialization of indexes to byte arrays
###########################################

def serialize_index(index):
    """ convert an index to a numpy uint8 array  """
    writer = faiss.VectorIOWriter()
    faiss.write_index(index, writer)
    return faiss.vector_to_array(writer.data)

def deserialize_index(data):
    reader = faiss.VectorIOReader()
    faiss.copy_array_to_vector(data, reader.data)
    return faiss.read_index(reader)

Eureka!