add (overwrite with) mypy stubs, if available

stdlib/3/struct.pyi

@@ -0,0 +1,30 @@
+# Stubs for struct
+
+# Based on http://docs.python.org/3.2/library/struct.html
+
+from typing import overload, Any, AnyStr, Tuple
+
+class error(Exception): ...
+
+def pack(fmt: AnyStr, *v: Any) -> bytes: ...
+# TODO buffer type
+def pack_into(fmt: AnyStr, buffer: Any, offset: int, *v: Any) -> None: ...
+
+# TODO buffer type
+def unpack(fmt: AnyStr, buffer: Any) -> Tuple[Any, ...]: ...
+def unpack_from(fmt: AnyStr, buffer: Any, offset: int = 0) -> Tuple[Any, ...]: ...
+
+def calcsize(fmt: AnyStr) -> int: ...
+
+class Struct:
+    format = b''
+    size = 0
+
+    def __init__(self, format: AnyStr) -> None: ...
+
+    def pack(self, *v: Any) -> bytes: ...
+    # TODO buffer type
+    def pack_into(self, buffer: Any, offset: int, *v: Any) -> None: ...
+    # TODO buffer type
+    def unpack(self, buffer: Any) -> Tuple[Any, ...]: ...
+    def unpack_from(self, buffer: Any, offset: int = 0) -> Tuple[Any, ...]: ...