<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def var(self):
 """ Variance value as a result of an uncertainty calculation """

        mn = self.mean
        vr = np.mean((self._mcpts - mn) ** 2)
        return vr