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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 get_array(self, period):
 """ Get the value of the variable for the given period. If the value is not known, return ``None``. """

        if self.variable.is_neutralized:
            return self.default_array()
        value = self._memory_storage.get(period)
        if value is not None:
            return value
        if self._disk_storage:
            return self._disk_storage.get(period)