fix(python): correct type annotations in EmbeddingFunctionRegistry (#2478)

- Fix register() method's alias parameter type from 'str = None' to
'Optional[str] = None'
- Add return type annotation 'Type[EmbeddingFunction]' to get() method
- Import Type from typing module for proper type hints

python/python/lancedb/embeddings/registry.py

@@ -2,7 +2,7 @@
 # SPDX-FileCopyrightText: Copyright The LanceDB Authors
 
 import json
-from typing import Dict, Optional
+from typing import Dict, Optional, Type
 
 from .base import EmbeddingFunction, EmbeddingFunctionConfig
 
@@ -43,7 +43,7 @@ class EmbeddingFunctionRegistry:
         self._functions = {}
         self._variables = {}
 
-    def register(self, alias: str = None):
+    def register(self, alias: Optional[str] = None):
         """
         This creates a decorator that can be used to register
         an EmbeddingFunction.
@@ -75,7 +75,7 @@ class EmbeddingFunctionRegistry:
         """
         self._functions = {}
 
-    def get(self, name: str):
+    def get(self, name: str) -> Type[EmbeddingFunction]:
         """
         Fetch an embedding function class by name