diff --git a/requests/sessions.py b/requests/sessions.py
index a4ca2719..659c1f06 100644
--- a/requests/sessions.py
+++ b/requests/sessions.py
@@ -353,7 +353,7 @@ class Session(SessionRedirectMixin):
       >>>     s.get('http://httpbin.org/get')
       <Response [200]>
     """
-    __attrs__ = [
+    __slots__ = [
         'headers',
         'cookies',
         'auth',
@@ -369,6 +369,8 @@ class Session(SessionRedirectMixin):
         'max_redirects',
     ]
 
+    __slots__
+
     def __init__(self):
         # : A case-insensitive dictionary of headers to be sent on each
         #: :class:`Request <Request>` sent from this
@@ -735,18 +737,9 @@ class Session(SessionRedirectMixin):
             self.adapters[key] = self.adapters.pop(key)
 
     def __getstate__(self):
-        state = {attr: getattr(self, attr, None) for attr in self.__attrs__}
+        state = {attr: getattr(self, attr, None) for attr in self.__slots__}
         return state
 
     def __setstate__(self, state):
         for attr, value in state.items():
             setattr(self, attr, value)
-
-
-def session():
-    """
-    Returns a :class:`Session` for context-management.
-
-    :rtype: Session
-    """
-    return Session()
diff --git a/requests/structures.py b/requests/structures.py
index 59d4645e..c88d744d 100644
--- a/requests/structures.py
+++ b/requests/structures.py
@@ -37,7 +37,6 @@ class CaseInsensitiveDict(collections.MutableMapping):
     operations are given keys that have equal ``.lower()``s, the
     behavior is undefined.
     """
-
     __slots__ = ('_store')
 
     def __init__(self, data=None, **kwargs):
@@ -98,7 +97,6 @@ class HTTPHeaderDict(CaseInsensitiveDict):
         self.extend({} if data is None else data, **kwargs)
 
 
-    #
     # We'll store tuples in the internal dictionary, but present them as a
     # concatenated string when we use item access methods.
     #