Deduplicate helpers & fix lint issues from #1099 (#1107)

tests/helpers.py

+from io import BytesIO
 from itertools import product
 import random
 from typing import Any, List
@@ -7,6 +8,25 @@ import torch
 test_dims_rng = random.Random(42)
 
 
+TRUE_FALSE = (True, False)
+BOOLEAN_TRIPLES = list(product(TRUE_FALSE, repeat=3))  # all combinations of (bool, bool, bool)
+BOOLEAN_TUPLES = list(product(TRUE_FALSE, repeat=2))  # all combinations of (bool, bool)
+
+
+def torch_save_to_buffer(obj):
+    buffer = BytesIO()
+    torch.save(obj, buffer)
+    buffer.seek(0)
+    return buffer
+
+
+def torch_load_from_buffer(buffer):
+    buffer.seek(0)
+    obj = torch.load(buffer)
+    buffer.seek(0)
+    return obj
+
+
 def get_test_dims(min: int, max: int, *, n: int) -> List[int]:
     return [test_dims_rng.randint(min, max) for _ in range(n)]
 
@@ -42,10 +62,3 @@ DTYPE_NAMES = {
 
 def describe_dtype(dtype: torch.dtype) -> str:
     return DTYPE_NAMES.get(dtype) or str(dtype).rpartition(".")[2]
-
-
-TRUE_FALSE = (True, False)
-BOOLEAN_TRIPLES = list(
-    product(TRUE_FALSE, repeat=3)
-)  # all combinations of (bool, bool, bool)
-BOOLEAN_TUPLES = list(product(TRUE_FALSE, repeat=2))  # all combinations of (bool, bool)

tests/test_linear4bit.py

 import copy
-from io import BytesIO
 import os
 import pickle
 from tempfile import TemporaryDirectory
@@ -8,7 +7,7 @@ import pytest
 import torch
 
 import bitsandbytes as bnb
-from tests.helpers import TRUE_FALSE
+from tests.helpers import TRUE_FALSE, torch_load_from_buffer, torch_save_to_buffer
 
 storage = {
     "uint8": torch.uint8,
@@ -17,17 +16,6 @@ storage = {
     "float32": torch.float32,
 }
 
-def torch_save_to_buffer(obj):
-    buffer = BytesIO()
-    torch.save(obj, buffer)
-    buffer.seek(0)
-    return buffer
-
-def torch_load_from_buffer(buffer):
-    buffer.seek(0)
-    obj = torch.load(buffer)
-    buffer.seek(0)
-    return obj
 
 @pytest.mark.parametrize("quant_storage", ["uint8", "float16", "bfloat16", "float32"])
 @pytest.mark.parametrize("bias", TRUE_FALSE)

tests/test_linear8bitlt.py

 from contextlib import nullcontext
-from io import BytesIO
 import os
 from tempfile import TemporaryDirectory
 
@@ -10,7 +9,12 @@ import bitsandbytes as bnb
 from bitsandbytes import functional as F
 from bitsandbytes.autograd import get_inverse_transform_indices, undo_layout
 from bitsandbytes.nn.modules import Linear8bitLt
-from tests.helpers import TRUE_FALSE, id_formatter
+from tests.helpers import (
+    TRUE_FALSE,
+    id_formatter,
+    torch_load_from_buffer,
+    torch_save_to_buffer,
+)
 
 # contributed by Alex Borzunov, see:
 # https://github.com/bigscience-workshop/petals/blob/main/tests/test_linear8bitlt.py
@@ -66,17 +70,6 @@ def test_linear_no_igemmlt():
     assert linear_custom.state.CB is not None
     assert linear_custom.state.CxB is None
 
-def torch_save_to_buffer(obj):
-    buffer = BytesIO()
-    torch.save(obj, buffer)
-    buffer.seek(0)
-    return buffer
-
-def torch_load_from_buffer(buffer):
-    buffer.seek(0)
-    obj = torch.load(buffer)
-    buffer.seek(0)
-    return obj
 
 @pytest.mark.parametrize("has_fp16_weights", TRUE_FALSE, ids=id_formatter("has_fp16_weights"))
 @pytest.mark.parametrize("serialize_before_forward", TRUE_FALSE, ids=id_formatter("serialize_before_forward"))