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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 get_last_block(working_dir):
 """ Get the last block processed Return the integer on success Return None on error """


    # make this usable even if we haven't explicitly configured virtualchain 
    impl = sys.modules[__name__]
    return BlockstackDB.get_lastblock(impl, working_dir)