ref: refactor extension_registry better exception handling, naming and added function type

Author: giospada

src/substrait/builders/type.py

@@ -223,6 +223,16 @@ def precision_timestamp_tz(precision: int, nullable=True) -> stt.Type:
     )
 
 
+def timestamp(nullable=True) -> stt.Type:
+    return stt.Type(
+        timestamp=stt.Type.Timestamp(
+            nullability=stt.Type.NULLABILITY_NULLABLE
+            if nullable
+            else stt.Type.NULLABILITY_REQUIRED,
+        )
+    )
+
+
 def struct(types: Iterable[stt.Type], nullable=True) -> stt.Type:
     return stt.Type(
         struct=stt.Type.Struct(