human
Solve the following python programming problem given the following code:
@ testing.skip_if ((lambda : testing.against ('oracle')), 'Test has an empty insert in it at the moment') 
def test_columns_single_inheritance_conflict_resolution(self) : 
    'Test that a declared_attr can return the existing column and it will
        be ignored.  this allows conditional columns to be added.

        See [ticket:2472].

        ' 
    class Person (Base) : 
        __tablename__ = 'person' 
        id = Column (Integer, primary_key = True) 
class Mixin (object) : 
        @ declared_attr 
        def target_id(cls) : 
            return cls.__table__.c.get ('target_id', Column (Integer, ForeignKey ('other.id'))) 
@ declared_attr 
        def target(cls) : 
            return relationship ('Other') 
class Engineer (Mixin, Person) : 
        'single table inheritance' 
class Manager (Mixin, Person) : 
        'single table inheritance' 
class Other (Base) : 
        __tablename__ = 'other' 
        id = Column (Integer, primary_key = True) 
is_ (Engineer.target_id.property.columns [0], Person.__table__.c.target_id) 
    is_ (Manager.target_id.property.columns [0], Person.__table__.c.target_id) 
    Base.metadata.create_all () 
    session = Session () 
    (o1, o2) = (Other (), Other ()) 
    session.add_all ([Engineer (target = o1), Manager (target = o2), Manager (target = o2)]) 
    session.commit () 
    eq_ (session.query (Engineer).first ().target, o1) 

    
    

    Fix the buggy line: session.add_all ([Engineer (target = o1), Manager (target = o2), Manager (target = o2)])
assistant
#Here is Python code to fix the buggy line: session.

session.add_all ([Engineer (target = o1), Manager (target = o2), Manager (target = o1)])