Simplify explanation of multiset operations by removing restrictions on negative inputs.
diff --git a/Lib/collections.py b/Lib/collections.py
index a853076..eb13f4d 100644
--- a/Lib/collections.py
+++ b/Lib/collections.py
@@ -312,8 +312,8 @@
if not isinstance(other, Counter):
return NotImplemented
result = Counter()
- for elem, count in self.iteritems():
- newcount = count - other[elem]
+ for elem in set(self) | set(other):
+ newcount = self[elem] - other[elem]
if newcount > 0:
result[elem] = newcount
return result