Fix an import in combo_model.py

combo/combo_model.py

@@ -22,6 +22,7 @@ from combo.data import Instance
 from combo.data.batch import Batch
 from combo.data.dataset_loaders.dataset_loader import TensorDict
 from combo.nn import utils
+from combo.predictors import Predictor
 
 
 @Registry.register("semantic_multitask")
@@ -42,7 +43,7 @@ class ComboModel(Model, FromParameters):
                  lemmatizer: LemmatizerModel = None,
                  upos_tagger: MorphologicalFeatures = None,
                  xpos_tagger: MorphologicalFeatures = None,
-                 semantic_relation: base.Predictor = None,
+                 semantic_relation: Predictor = None,
                  morphological_feat: MorphologicalFeatures = None,
                  dependency_relation: DependencyRelationModel = None,
                  enhanced_dependency_relation: DependencyRelationModel = None,