first add files

lib/Crypto/Cipher/_mode_cbc.pyi

@@ -0,0 +1,25 @@
+from typing import Union, overload
+
+from Crypto.Util._raw_api import SmartPointer
+
+Buffer = Union[bytes, bytearray, memoryview]
+
+__all__ = ['CbcMode']
+
+class CbcMode(object):
+    block_size: int
+    iv: Buffer
+    IV: Buffer
+
+    def __init__(self,
+                 block_cipher: SmartPointer,
+                 iv: Buffer) -> None: ...
+    @overload
+    def encrypt(self, plaintext: Buffer) -> bytes: ...
+    @overload
+    def encrypt(self, plaintext: Buffer, output: Union[bytearray, memoryview]) -> None: ...
+    @overload
+    def decrypt(self, plaintext: Buffer) -> bytes: ...
+    @overload
+    def decrypt(self, plaintext: Buffer, output: Union[bytearray, memoryview]) -> None: ...
+