Remove duplicate PairTest from pyutils/__init__.py

Author: jhgg

graphql/core/pyutils/__init__.py

@@ -1,18 +0,0 @@
-class PairSet(object):
-    def __init__(self):
-        self._data = set()
-
-    def __contains__(self, item):
-        return item in self._data
-
-    def has(self, a, b):
-        return (a, b) in self._data
-
-    def add(self, a, b):
-        self._data.add((a, b))
-        self._data.add((b, a))
-        return self
-
-    def remove(self, a, b):
-        self._data.discard((a, b))
-        self._data.discard((b, a))