Fix to_dict and from_dict of Multilabel such that to_dict outputs a json serializable object (using Label.to_dict()) (#5257)

haystack/schema.py

@@ -633,7 +633,7 @@ def is_positive_label(label):
 
 
 class MultiLabel:
-    def __init__(self, labels: List[Label], drop_negative_labels=False, drop_no_answers=False):
+    def __init__(self, labels: List[Label], drop_negative_labels: bool = False, drop_no_answers: bool = False):
         """
         There are often multiple `Labels` associated with a single query. For example, there can be multiple annotated
         answers for one question or multiple documents contain the information you want for a query.
@@ -753,12 +753,17 @@ class MultiLabel:
 
     def to_dict(self):
         # convert internal attribute names to property names
-        return {k[1:] if k[0] == "_" else k: v for k, v in vars(self).items()}
+        result = {k[1:] if k[0] == "_" else k: v for k, v in vars(self).items()}
+        # convert Label object to dict
+        result["labels"] = [label.to_dict() for label in result["labels"]]
+        return result
 
     @classmethod
     def from_dict(cls, dict: Dict):
         # exclude extra arguments
-        return cls(**{k: v for k, v in dict.items() if k in inspect.signature(cls).parameters})
+        inputs = {k: v for k, v in dict.items() if k in inspect.signature(cls).parameters}
+        inputs["labels"] = [Label.from_dict(label) for label in inputs["labels"]]
+        return cls(**inputs)
 
     def to_json(self):
         return json.dumps(self.to_dict(), default=pydantic_encoder)
@@ -769,7 +774,6 @@ class MultiLabel:
             dict_data = json.loads(data)
         else:
             dict_data = data
-        dict_data["labels"] = [Label.from_dict(l) for l in dict_data["labels"]]
         return cls.from_dict(dict_data)
 
     def __eq__(self, other):

test/others/test_schema.py

@@ -932,6 +932,52 @@ def test_multilabel_serialization():
     assert json_deserialized_multilabel.labels[0] == label
 
 
+@pytest.mark.unit
+def test_table_multilabel_serialization():
+    tabel_label_dict = {
+        "id": "011079cf-c93f-49e6-83bb-42cd850dce12",
+        "query": "What is the first number?",
+        "document": {
+            "content": [["col1", "col2"], [1, 3], [2, 4]],
+            "content_type": "table",
+            "id": "table1",
+            "meta": {},
+            "score": None,
+            "embedding": None,
+        },
+        "is_correct_answer": True,
+        "is_correct_document": True,
+        "origin": "user-feedback",
+        "answer": {
+            "answer": "1",
+            "type": "extractive",
+            "score": None,
+            "context": [["col1", "col2"], [1, 3], [2, 4]],
+            "offsets_in_document": [{"row": 0, "col": 0}],
+            "offsets_in_context": [{"row": 0, "col": 0}],
+            "document_ids": ["table1"],
+            "meta": {},
+        },
+        "no_answer": False,
+        "pipeline_id": None,
+        "created_at": "2022-07-22T13:29:33.699781+00:00",
+        "updated_at": "2022-07-22T13:29:33.784895+00:00",
+        "meta": {"answer_id": "374394", "document_id": "604995", "question_id": "345530"},
+        "filters": None,
+    }
+
+    label = Label.from_dict(tabel_label_dict)
+    original_multilabel = MultiLabel([label])
+
+    deserialized_multilabel = MultiLabel.from_dict(original_multilabel.to_dict())
+    assert deserialized_multilabel == original_multilabel
+    assert deserialized_multilabel.labels[0] == label
+
+    json_deserialized_multilabel = MultiLabel.from_json(original_multilabel.to_json())
+    assert json_deserialized_multilabel == original_multilabel
+    assert json_deserialized_multilabel.labels[0] == label
+
+
 @pytest.mark.unit
 def test_span_in():
     assert 10 in Span(5, 15)