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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 imports(symbol_file, input_names, param_file=None, ctx=None):
 """Import model previously saved by `HybridBlock.export` or `Module.save_checkpoint` as a SymbolBlock for use in Gluon. Parameters symbol_file : str Path to symbol file. input_names : list of str List of input variable names param_file : str, optional Path to parameter file. ctx : Context, default None The context to initialize SymbolBlock on. Returns ------- SymbolBlock SymbolBlock loaded from symbol and parameter files. Examples -------- """

        sym = symbol.load(symbol_file)
        if isinstance(input_names, str):
            input_names = [input_names]
        inputs = [symbol.var(i) for i in input_names]
        ret = SymbolBlock(sym, inputs)
        if param_file is not None:
            ret.collect_params().load(param_file, ctx=ctx)
        return ret