Add stub type to register multiple logical types mapping to same language type.

Author: claudevdm

sdks/python/apache_beam/typehints/schemas.py

@@ -863,8 +863,15 @@ def _from_typing(cls, typ):
                                     ('micros', np.int64)])
 
 
+class MillisTimestamp():
+  """A stub type used during registration to allow multiple logical types to
+  use the same Timestamp language type but with different to_language_type.
+  """
+  pass
+
+
 @LogicalType.register_logical_type
-class MillisInstant(NoArgumentLogicalType[Timestamp, np.int64]):
+class MillisInstant(NoArgumentLogicalType[MillisTimestamp, np.int64]):
   """Millisecond-precision instant logical type handles values consistent with
   that encoded by ``InstantCoder`` in the Java SDK.
 
@@ -890,7 +897,7 @@ def urn(cls):
 
   @classmethod
   def language_type(cls):
-    return Timestamp
+    return MillisTimestamp
 
   def to_language_type(self, value):
     # type: (np.int64) -> Timestamp