Added type hints

src/PIL/Image.py

@@ -3507,7 +3507,7 @@ def registered_extensions():
     return EXTENSION
 
 
-def register_decoder(name, decoder):
+def register_decoder(name: str, decoder) -> None:
     """
     Registers an image decoder.  This function should not be
     used in application code.

src/PIL/ImageFile.py

@@ -713,7 +713,7 @@ class PyDecoder(PyCodec):
         msg = "unavailable in base decoder"
         raise NotImplementedError(msg)
 
-    def set_as_raw(self, data, rawmode=None):
+    def set_as_raw(self, data: bytes, rawmode = None) -> None:
         """
         Convenience method to set the internal image from a stream of raw data
 

src/PIL/MspImagePlugin.py

@@ -35,7 +35,7 @@ from ._binary import o16le as o16
 # read MSP files
 
 
-def _accept(prefix):
+def _accept(prefix: bytes) -> bool:
     return prefix[:4] in [b"DanM", b"LinS"]
 
 
@@ -48,8 +48,10 @@ class MspImageFile(ImageFile.ImageFile):
     format = "MSP"
     format_description = "Windows Paint"
 
-    def _open(self):
+    def _open(self) -> None:
         # Header
+        assert self.fp is not None
+
         s = self.fp.read(32)
         if not _accept(s):
             msg = "not an MSP file"
@@ -109,7 +111,9 @@ class MspDecoder(ImageFile.PyDecoder):
 
     _pulls_fd = True
 
-    def decode(self, buffer):
+    def decode(self, buffer: bytes) -> tuple[int, int]:
+        assert self.fd is not None
+
         img = io.BytesIO()
         blank_line = bytearray((0xFF,) * ((self.state.xsize + 7) // 8))
         try:
@@ -159,7 +163,7 @@ Image.register_decoder("MSP", MspDecoder)
 # write MSP files (uncompressed only)
 
 
-def _save(im, fp, filename):
+def _save(im: Image.Image, fp: io.BytesIO, filename: str) -> None:
     if im.mode != "1":
         msg = f"cannot write mode {im.mode} as MSP"
         raise OSError(msg)