Get rid of operator usage

Bug: #295 (comment)

docs/index.rst

@@ -21,7 +21,6 @@ method calls.
 
 .. testsetup:: *
 
-   import operator
    from cachetools import cached, cachedmethod, LRUCache, TLRUCache, TTLCache
 
    from unittest import mock
@@ -422,7 +421,7 @@ often called with the same arguments:
           def __init__(self, cachesize):
               self.cache = LRUCache(maxsize=cachesize)
 
-          @cachedmethod(operator.attrgetter('cache'))
+          @cachedmethod(lambda self: self.cache)
           def get(self, num):
               """Retrieve text of a Python Enhancement Proposal"""
               url = 'http://www.python.org/dev/peps/pep-%04d/' % num

tests/test_cachedmethod.py

@@ -1,4 +1,3 @@
-import operator
 import unittest
 
 from cachetools import LRUCache, cachedmethod, keys
@@ -9,13 +8,13 @@ def __init__(self, cache, count=0):
         self.cache = cache
         self.count = count
 
-    @cachedmethod(operator.attrgetter("cache"))
+    @cachedmethod(lambda self: self.cache)
     def get(self, value):
         count = self.count
         self.count += 1
         return count
 
-    @cachedmethod(operator.attrgetter("cache"), key=keys.typedkey)
+    @cachedmethod(lambda self: self.cache, key=keys.typedkey)
     def get_typed(self, value):
         count = self.count
         self.count += 1
@@ -27,7 +26,7 @@ def __init__(self, cache):
         self.cache = cache
         self.count = 0
 
-    @cachedmethod(operator.attrgetter("cache"), lock=lambda self: self)
+    @cachedmethod(lambda self: self.cache, lock=lambda self: self)
     def get(self, value):
         return self.count
 
@@ -42,11 +41,11 @@ class Unhashable:
     def __init__(self, cache):
         self.cache = cache
 
-    @cachedmethod(operator.attrgetter("cache"))
+    @cachedmethod(lambda self: self.cache)
     def get_default(self, value):
         return value
 
-    @cachedmethod(operator.attrgetter("cache"), key=keys.hashkey)
+    @cachedmethod(lambda self: self.cache, key=keys.hashkey)
     def get_hashkey(self, value):
         return value