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