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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 __set_formula(self, formula):
 """ Sets a formula in this cell. Any cell value can be set using this method. Actual formulas must start with an equal sign. """

        array = ((self._clean_formula(formula),),)
        return self._get_target().setFormulaArray(array)