remove too-clever lazy dictionary

common/lib/xmodule/lazy_dict.py

-from collections import MutableMapping
-
-class LazyLoadingDict(MutableMapping):
-    """
-    A dictionary object that lazily loads its contents from a provided
-    function on reads (of members that haven't already been set).
-    """
-
-    def __init__(self, loader):
-        '''
-        On the first read from this dictionary, it will call loader() to
-        populate its contents.  loader() must return something dict-like. Any
-        elements set before the first read will be preserved.
-        '''
-        self._contents = {}
-        self._loaded = False
-        self._loader = loader
-        self._deleted = set()
-
-    def __getitem__(self, name):
-        if not (self._loaded or name in self._contents or name in self._deleted):
-            self.load()
-
-        return self._contents[name]
-
-    def __setitem__(self, name, value):
-        self._contents[name] = value
-        self._deleted.discard(name)
-
-    def __delitem__(self, name):
-        del self._contents[name]
-        self._deleted.add(name)
-
-    def __contains__(self, name):
-        self.load()
-        return name in self._contents
-
-    def __len__(self):
-        self.load()
-        return len(self._contents)
-
-    def __iter__(self):
-        self.load()
-        return iter(self._contents)
-
-    def __repr__(self):
-        self.load()
-        return repr(self._contents)
-
-    def load(self):
-        if self._loaded:
-            return
-
-        loaded_contents = self._loader()
-        loaded_contents.update(self._contents)
-        self._contents = loaded_contents
-        self._loaded = True
-