<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def date_from_number(self, value):
 """ Converts a float value to corresponding datetime instance. """

        if not isinstance(value, numbers.Real):
            return None
        delta = datetime.timedelta(days=value)
        return self._null_date + delta