Update TypeError on GpuMemoryStore

Author: maxrjones

src/zarr/storage/_memory.py

@@ -233,8 +233,9 @@ async def set(self, key: str, value: Buffer, byte_range: tuple[int, int] | None
         self._check_writable()
         assert isinstance(key, str)
         if not isinstance(value, Buffer):
-            raise TypeError(f"Expected Buffer. Got {type(value)}.")
-
+            raise TypeError(
+                f"GpuMemoryStore.set(): `value` must be a Buffer instance. Got an instance of {type(value)} instead."
+            )
         # Convert to gpu.Buffer
         gpu_value = value if isinstance(value, gpu.Buffer) else gpu.Buffer.from_buffer(value)
         await super().set(key, gpu_value, byte_range=byte_range)