Update a record to the table 
        emp = Employee(emp_id=1, name='John Doe', sex='Female')
        updated = Session().add(emp)
        Returns a bool or raises mysql.Error exception

def update(self, instance):
        '''
        Update a record to the table 
        emp = Employee(emp_id=1, name='John Doe', sex='Female')
        updated = Session().add(emp)
        Returns a bool or raises mysql.Error exception
        '''

        if not self.exists(instance.__class__, instance.id):
            print("Cant update a value that does not exist")
            return False

        instance_dict = vars(instance)

        table = instance.__class__.__name__.lower()
        keys = ", ".join(instance_dict.keys())
        values = tuple(instance_dict.values())

        SQL = """UPDATE {} SET """.format(table)

        for key, value in instance_dict.items():
            SQL += """ %s = "%s" ,""" % (key, value)

        SQL = SQL[:-1] + """ WHERE id = "{}" """.format(instance.id)

        if self.DEBUG: print(SQL)

        try:
            with Session(self.settings) as conn:
                c = conn.cursor()
                c.execute(SQL)
                conn.commit()
                return True
        except Exception as e:
            raise e