Add missing stubs for bz2

stdlib/2and3/bz2.pyi

@@ -1,6 +1,34 @@
 # Stubs for bz2
 
-# TODO: This stub is incomplete
+from typing import Any, BinaryIO, TextIO, IO, Union
 
 def compress(data: bytes, compresslevel: int = ...) -> bytes: ...
 def decompress(data: bytes) -> bytes: ...
+
+def open(filename: Union[str, bytes, IO[Any]],
+         mode: str = 'rb',
+         encoding: str = None,
+         errors: str = None,
+         newline: str = None) -> Union[TextIO, BinaryIO]: ...
+
+class BZ2File(BinaryIO):
+    def __init__(self,
+                 filename: Union[str, bytes, IO[Any]],
+                 mode: str = "r",
+                 buffering: Any = None,
+                 compresslevel: int = 9) -> None: ...
+
+class BZ2Compressor(object):
+    def __init__(self, compresslevel: int = 9) -> None: ...
+    def compress(self, data: bytes) -> bytes: ...
+    def flush(self) -> bytes: ...
+
+
+class BZ2Decompressor(object):
+    def decompress(self, data: bytes) -> bytes: ...
+    @property
+    def eof(self) -> bool: ...
+    @property
+    def needs_input(self) -> bool: ...
+    @property
+    def unused_data(self) -> bytes: ...