Cache getting SourceInfo for a class

The inspect calls invoked in this method are not very cheap, so this can be a nice speedup if called many times on the same class.

PiperOrigin-RevId: 670111306

seqio/dataset_providers.py

@@ -95,6 +95,7 @@ class SourceInfo:
   line_number: Optional[int] = None
 
   @classmethod
+  @functools.lru_cache(maxsize=None)
   def for_class(cls, klass) -> SourceInfo:
     """Returns info about where the given class was defined."""
     try: