Update docstring for BZ2File.__init__().
diff --git a/Lib/bz2.py b/Lib/bz2.py
index 36e5558..5c228f9 100644
--- a/Lib/bz2.py
+++ b/Lib/bz2.py
@@ -47,13 +47,17 @@
the file object given by fileobj. Exactly one of these two
parameters should be provided.
- mode can be 'r' for reading (default), or 'w' for writing.
+ mode can be 'r' for reading (default), 'w' for (over)writing, or
+ 'a' for appending.
buffering is ignored. Its use is deprecated.
- If mode is 'w', compresslevel can be a number between 1 and 9
- specifying the level of compression: 1 produces the least
+ If mode is 'w' or 'a', compresslevel can be a number between 1
+ and 9 specifying the level of compression: 1 produces the least
compression, and 9 (default) produces the most compression.
+
+ If mode is 'r', the input file may be the concatenation of
+ multiple compressed streams.
"""
# This lock must be recursive, so that BufferedIOBase's
# readline(), readlines() and writelines() don't deadlock.