def migrate_references(row, migrated, target, proc_hash=nil)
      # migrate the owner
      migratable__migrate_owner(row, migrated, target, proc_hash)
      # migrate the remaining attributes
      migratable__set_nonowner_references(migratable_independent_attributes, row, migrated, proc_hash)
      migratable__set_nonowner_references(self.class.unidirectional_dependent_attributes, row, migrated, proc_hash)
    end
def migrate_references(row, migrated, target, proc_hash=nil)
      # migrate the owner
      migratable__migrate_owner(row, migrated, target, proc_hash)
      # migrate the remaining attributes
      migratable__set_nonowner_references(migratable_independent_attributes, row, migrated, proc_hash)
      migratable__set_nonowner_references(self.class.unidirectional_dependent_attributes, row, migrated, proc_hash)
    end
Migrates this domain object's migratable references. This method is called by the
 Migrator and should not be overridden by subclasses. Subclasses tailor
 individual reference attribute migration by defining a +migrate_+_attribute_ method
 for the _attribute_ to modify.

 The migratable reference attributes consist of the non-collection saved independent
 attributes and the unidirectional dependent attributes which don't already have a value.
 For each such migratable attribute, if there is a single instance of the attribute
 type in the given migrated domain objects, then the attribute is set to that
 migrated instance.

 If the attribute is associated with a method in proc_hash, then that method is called
 on the migrated instance and input row. The attribute is set to the method return value.
 proc_hash includes an entry for each +migrate_+_attribute_ method defined by this
 Resource's class.

 @param [{Symbol => Object}] row the input row field => value hash
 @param [<Resource>] migrated the migrated instances, including this Resource
 @param [Class] target the migration target class
 @param [{Symbol => Proc}, nil] proc_hash a hash that associates this domain object's
   attributes to a migration shim block