diff --git a/examples/summarization/run_summarization.py b/examples/summarization/run_summarization.py
index 1917ca30..4afa97b5 100644
--- a/examples/summarization/run_summarization.py
+++ b/examples/summarization/run_summarization.py
@@ -184,7 +184,10 @@ def save_rouge_scores(str_scores):
 def build_data_iterator(args, tokenizer):
     dataset = load_and_cache_examples(args, tokenizer)
     sampler = SequentialSampler(dataset)
-    collate_fn = lambda data: collate(data, tokenizer, block_size=512, device=args.device)
+
+    def collate_fn(data):
+        return collate(data, tokenizer, block_size=512, device=args.device)
+
     iterator = DataLoader(dataset, sampler=sampler, batch_size=args.batch_size, collate_fn=collate_fn,)
 
     return iterator
diff --git a/transformers/commands/serving.py b/transformers/commands/serving.py
index 5d48cc0b..04dea67b 100644
--- a/transformers/commands/serving.py
+++ b/transformers/commands/serving.py
@@ -15,7 +15,10 @@ try:
     _serve_dependancies_installed = True
 except (ImportError, AttributeError):
     BaseModel = object
-    Body = lambda *x, **y: None
+
+    def Body(*x, **y):
+        pass
+
     _serve_dependancies_installed = False
 
 
diff --git a/transformers/modeling_utils.py b/transformers/modeling_utils.py
index 245a1afa..79b7dafc 100644
--- a/transformers/modeling_utils.py
+++ b/transformers/modeling_utils.py
@@ -77,7 +77,6 @@ class PreTrainedModel(nn.Module):
     """
     config_class = None
     pretrained_model_archive_map = {}
-    load_tf_weights = lambda model, config, path: None
     base_model_prefix = ""
 
     @property