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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 copy_file(self, src_path, file_name, key=None):
 """Copies a file unmodified to a location inside the ouput directory. Parameters src_path: str Path to the src file file_name: str name of the destination file """

        path = os.path.join(self._directories[key], file_name)
        shutil.copyfile(src_path, path)