Minor changes

fedot/core/data/merge/data_merger.py

@@ -170,9 +170,10 @@ def merge_predicts(self, predicts: List[np.array]) -> np.array:
         if any(len(pred.shape) > 2 for pred in predicts):
             raise ValueError('Merge of arrays with more than 2 dimensions is not supported')
         if len(predicts) > 1:
+            predicts = [predict.astype(str) for predict in predicts]
             result = predicts[0]
             for i in range(1, len(predicts)):
-                result += ' ' + predicts[i]
+                result = np.core.defchararray.add(result, predicts[i])
             return result
         return predicts[0]
 

test/unit/data/test_data_merge_text.py

@@ -36,6 +36,8 @@ def generate_output_texts(length=10, num_columns=1):
     return OutputData(idx,  task, data_type, features=features, predict=features, target=None)
 
 
+# len(params) is a number of input arrays, each element of params - number of columns in the corresponding array
+# FEDOT supports merging of text data with 1 column only, so ValueError is expected for (2, 1) and (2, 3, 1) cases
 @pytest.fixture(params=[(1,), (1, 1), (1, 1, 1), (2, 1), (2, 3, 1)],
                 ids=lambda cols: f'texts with {cols} columns')
 def output_texts(request):