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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 create_constant(self, expression, *, verbose=True):
 """Append a constant to the stored list. Parameters expression : str Expression for the new constant. verbose : boolean (optional) Toggle talkback. Default is True See Also -------- set_constants Remove and replace all constants. remove_constant Remove an individual constant. """

        if expression in self.constant_expressions:
            wt_exceptions.ObjectExistsWarning.warn(expression)
            return self.constants[self.constant_expressions.index(expression)]
        constant = Constant(self, expression)
        if constant.units is None:
            constant.convert(constant.variables[0].units)
        self._constants.append(constant)
        self.flush()
        self._on_constants_updated()
        if verbose:
            print("Constant '{}' added".format(constant.expression))
        return constant