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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 save(self, commit=False):
 """Save the changes to the model. If the model has not been persisted then it adds the model to the declared session. Then it flushes the object session and optionally commits it. """

        if not has_identity(self):
            # Object has not been persisted to the database.
            session.add(self)

        if commit:
            # Commit the session as requested.
            session.commit()

        else:
            # Just flush the session; do not commit.
            session.flush()