<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def min_value(self):
 """ The minimum pixel value of the ``data`` within the source segment. """


        if self._is_completely_masked:
            return np.nan * self._data_unit
        else:
            return np.min(self.values)