Extract the finish check for profiler (pytorch#4519)

* Extract the finish check for profiler

Delete unused import and rearrange the import order.

* Add imports for win support

torch/autograd/profiler.py

@@ -1,11 +1,11 @@
-import torch
 import subprocess
 import os
 import sys
-import copy
-import tempfile
+import re
 import itertools
-from collections import defaultdict, namedtuple
+from collections import defaultdict
+
+import torch
 
 try:
     FileNotFoundError
@@ -202,27 +202,27 @@ def __str__(self):
             return '<unfinished torch.autograd.profile>'
         return str(self.function_events)
 
-    def table(self, sort_by=None):
+    def _check_finish(self):
         if self.function_events is None:
             raise RuntimeError("can't export a trace that didn't finish running")
+
+    def table(self, sort_by=None):
+        self._check_finish()
         return self.function_events.table(sort_by)
     table.__doc__ = EventList.table.__doc__
 
     def export_chrome_trace(self, path):
-        if self.function_events is None:
-            raise RuntimeError("can't export a trace that didn't finish running")
+        self._check_finish()
         return self.function_events.export_chrome_trace(path)
     export_chrome_trace.__doc__ = EventList.export_chrome_trace.__doc__
 
     def key_averages(self):
-        if self.function_events is None:
-            raise RuntimeError("can't average a trace that didn't finish running")
+        self._check_finish()
         return self.function_events.key_averages()
     key_averages.__doc__ = EventList.key_averages.__doc__
 
     def total_average(self):
-        if self.function_events is None:
-            raise RuntimeError("can't average a trace that didn't finish running")
+        self._check_finish()
         return self.function_events.total_average()
     total_average.__doc__ = EventList.total_average.__doc__