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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 add_file_arg(self, filename):
 """ Add a file argument to the executable. Arguments are appended after any options and their order is guaranteed. Also adds the file name to the list of required input data for this job. @param filename: file to add as argument. """

    self.__arguments.append(filename)
    if filename not in self.__input_files:
      self.__input_files.append(filename)