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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 ocrd_tool_tool_parse_params(ctx, parameters, json):
 """ Parse parameters with fallback to defaults and output as shell-eval'able assignments to params var. """

    if parameters is None or parameters == "":
        parameters = {}
    else:
        with open(parameters, 'r') as f:
            parameters = loads(f.read())
    parameterValidator = ParameterValidator(ctx.json['tools'][ctx.tool_name])
    report = parameterValidator.validate(parameters)
    if not report.is_valid:
        print(report.to_xml())
        sys.exit(1)
    if json:
        print(dumps(parameters))
    else:
        for k in parameters:
            print('params["%s"]="%s"' % (k, parameters[k]))