Required Files
- active_record/associations/association_proxy
- active_record/associations/association_collection
- active_record/associations/belongs_to_association
- active_record/associations/belongs_to_polymorphic_association
- active_record/associations/has_one_association
- active_record/associations/has_many_association
- active_record/associations/has_many_through_association
- active_record/associations/has_and_belongs_to_many_association
- active_record/deprecated_associations