Support cached_property for python version < 3.8 (#171)

Author: Xiuyu-Li

requirements.txt

@@ -0,0 +1,5 @@
+backports.cached_property
+numpy
+tqdm
+typing-extensions
+wheel

torchsparse/nn/modules/conv.py

@@ -1,7 +1,12 @@
 import math
-from functools import cached_property
+import sys
 from typing import Dict, List, Tuple, Union
 
+if sys.version_info >= (3, 8):
+    from functools import cached_property
+else:
+    from backports.cached_property import cached_property
+
 import numpy as np
 import torch
 from torch import nn