Deleted two duplicated paragraphs in the intro. Added mention of
UserDict and UserList and mixins in the intro. Fixed a typo.
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index e18dfcf..bb2140c 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -10,16 +10,10 @@
This module implements high-performance container datatypes. Currently,
there are two datatypes, :class:`deque` and :class:`defaultdict`, and
-one datatype factory function, :func:`namedtuple`.
-
-Besides the containers provided here, the optional :mod:`bsddb`
-module offers the ability to create in-memory or file based ordered
-dictionaries with string keys using the :meth:`bsddb.btopen` method.
-
-In addition to containers, the collections module provides some ABCs
-(abstract base classes) that can be used to test whether a class
-provides a particular interface, for example, is it hashable or
-a mapping.
+one datatype factory function, :func:`namedtuple`. This module also
+provides the :class:`UserDict` and :class:`UserList` classes which may
+be useful when inheriting directly from :class:`dict` or
+:class:`list` isn't convenient.
The specialized containers provided in this module provide alternatives
to Python's general purpose built-in containers, :class:`dict`,
@@ -29,9 +23,9 @@
dictionaries with string keys using the :meth:`bsddb.btopen` method.
In addition to containers, the collections module provides some ABCs
-(abstract base classes) that can be used to test whether a class
+(abstract base classes). These can be used to test whether a class
provides a particular interface, for example, is it hashable or
-a mapping.
+a mapping, and some of them can also be used as mixin classes.
ABCs - abstract base classes
----------------------------
@@ -114,7 +108,7 @@
Since some set operations create new sets, the default mixin methods need
a way to create new instances from an iterable. The class constructor is
assumed to have a signature in the form ``ClassName(iterable)``.
- That assumption is factored-out to a singleinternal classmethod called
+ That assumption is factored-out to a single internal classmethod called
:meth:`_from_iterable` which calls ``cls(iterable)`` to produce a new set.
If the :class:`Set` mixin is being used in a class with a different
constructor signature, you will need to override :meth:`from_iterable`