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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_arg(self, key, value, mask=False):
 """Add CLI Arg for the correct language. Args: key (string):
 The CLI Args key (e.g., --name). value (string):
 The CLI Args value (e.g., bob). mask (boolean, default:False):
 Indicates whether no mask value. """

        if self.lang == 'python':
            self._add_arg_python(key, value, mask)
        elif self.lang == 'java':
            self._add_arg_java(key, value, mask)