Classify invalid extensions properly.
@@ -1056,7 +1056,7 @@ class KgtkValue(KgtkFormat):
force self.valid to False.
"""
- if self.data_type is not None:
+ if self.data_type is None:
if not self.value.startswith("!"):
return False
# This is an extension, but for now, assume that all extensions are invalid.
