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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 db_create(cls, impl, working_dir):
 """ Create a sqlite3 db at the given path. Create all the tables and indexes we need. Returns a db connection on success Raises an exception on error """


        global VIRTUALCHAIN_DB_SCRIPT
       
        log.debug("Setup chain state in {}".format(working_dir))

        path = config.get_snapshots_filename(impl, working_dir)
        if os.path.exists( path ):
            raise Exception("Database {} already exists")

        lines = [l + ";" for l in VIRTUALCHAIN_DB_SCRIPT.split(";")]
        con = sqlite3.connect(path, isolation_level=None, timeout=2**30)

        for line in lines:
            con.execute(line)

        con.row_factory = StateEngine.db_row_factory
        return con