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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 db_value(self, value):
 """Convert the Arrow instance to a datetime for saving in the db."""

        if isinstance(value, string_types):
            value = arrow.get(value)

        if isinstance(value, arrow.Arrow):
            value = value.datetime

        return super(ArrowDateTimeField, self).db_value(value)