diff --git a/haystack/document_stores/mongodb_atlas.py b/haystack/document_stores/mongodb_atlas.py
index 8c572f54d2..28d64c5498 100644
--- a/haystack/document_stores/mongodb_atlas.py
+++ b/haystack/document_stores/mongodb_atlas.py
@@ -13,6 +13,7 @@
 
 with LazyImport("Run 'pip install farm-haystack[mongodb]'") as mongodb_import:
     import pymongo
+    import pymongo.collection.Collection
     from pymongo import InsertOne, ReplaceOne, UpdateOne
     from pymongo.driver_info import DriverInfo
 
diff --git a/haystack/modeling/model/language_model.py b/haystack/modeling/model/language_model.py
index e1f4028eba..5bf37771cc 100644
--- a/haystack/modeling/model/language_model.py
+++ b/haystack/modeling/model/language_model.py
@@ -18,26 +18,24 @@
 Thanks for the great work!
 """
 
-from typing import Type, Optional, Dict, Any, Union, List
-
-import re
 import json
 import logging
 import os
+import re
 from abc import ABC, abstractmethod
 from pathlib import Path
+from typing import Any, Dict, List, Optional, Type, Union
+
 import numpy as np
 import torch
-from torch import nn
 import transformers
-from transformers import PretrainedConfig, PreTrainedModel
-from transformers import AutoModel, AutoConfig
+from torch import nn
+from transformers import AutoConfig, AutoModel, PretrainedConfig, PreTrainedModel
 from transformers.modeling_utils import SequenceSummary
 
 from haystack.errors import ModelingError
 from haystack.modeling.utils import silence_transformers_logs
 
-
 logger = logging.getLogger(__name__)
 
 
@@ -213,8 +211,7 @@ def _pool_tokens(
     ):
         token_vecs = sequence_output.cpu().numpy()
         # we only take the aggregated value of non-padding tokens
-        padding_mask = padding_mask.cpu().numpy()
-        ignore_mask_2d = padding_mask == 0
+        ignore_mask_2d = padding_mask.cpu().numpy() == 0
         # sometimes we want to exclude the CLS token as well from our aggregation operation
         if ignore_first_token:
             ignore_mask_2d[:, 0] = True
diff --git a/haystack/modeling/model/prediction_head.py b/haystack/modeling/model/prediction_head.py
index df025b5cdd..74136ddf23 100644
--- a/haystack/modeling/model/prediction_head.py
+++ b/haystack/modeling/model/prediction_head.py
@@ -502,15 +502,14 @@ def logits_to_preds(
         # sorted_candidates.shape : (batch_size, max_seq_len^2, 2)
         start_indices = torch.div(flat_sorted_indices, max_seq_len, rounding_mode="trunc")
         end_indices = flat_sorted_indices % max_seq_len
-        sorted_candidates = torch.cat((start_indices, end_indices), dim=2)
 
         # Get the n_best candidate answers for each sample
-        sorted_candidates = sorted_candidates.cpu().numpy()
-        start_end_matrix = start_end_matrix.cpu().numpy()
+        sorted_candidates = torch.cat((start_indices, end_indices), dim=2).cpu().numpy()
+        start_end_matrix_array = start_end_matrix.cpu().numpy()
         for sample_idx in range(batch_size):
             sample_top_n = self.get_top_candidates(
                 sorted_candidates[sample_idx],
-                start_end_matrix[sample_idx],
+                start_end_matrix_array[sample_idx],
                 sample_idx,
                 start_matrix=start_matrix[sample_idx],
                 end_matrix=end_matrix[sample_idx],
diff --git a/haystack/utils/experiment_tracking.py b/haystack/utils/experiment_tracking.py
index 2a9f8d1ef4..21195449d7 100644
--- a/haystack/utils/experiment_tracking.py
+++ b/haystack/utils/experiment_tracking.py
@@ -213,7 +213,7 @@ def track_params(self, params: Dict[str, Any]):
 
     def track_artifacts(self, dir_path: Union[str, Path], artifact_path: Optional[str] = None):
         try:
-            mlflow.log_artifacts(dir_path, artifact_path)
+            mlflow.log_artifacts(str(dir_path), artifact_path)
         except ConnectionError:
             logger.warning("ConnectionError in logging artifacts to MLflow")
         except Exception as e: