update comments for _adjust_binner_for_upsample

Author: discort

pandas/core/resample.py

@@ -962,7 +962,10 @@ def _downsample(self, how, **kwargs):
         return self._wrap_result(result)
 
     def _adjust_binner_for_upsample(self, binner):
-        """ adjust our binner when upsampling """
+        """
+        Adjust our binner when upsampling.
+        The range of a new index should not be outside specified range
+        """
         if self.closed == 'right':
             binner = binner[1:]
         else:
@@ -1156,6 +1159,7 @@ def _get_binner_for_time(self):
 
     def _adjust_binner_for_upsample(self, binner):
         """ adjust our binner when upsampling """
+        # Just returning binner directly, GH 13022
         return binner