Check type of constraint using isinstance() rather than by type field

python/felis/tap.py

@@ -37,7 +37,7 @@
 
 from felis import datamodel
 
-from .datamodel import Constraint, Index, Schema, Table
+from .datamodel import Constraint, ForeignKeyConstraint, Index, Schema, Table
 from .types import FelisType
 
 __all__ = ["TapLoadingVisitor", "init_tables"]
@@ -480,10 +480,9 @@ def visit_constraint(self, constraint_obj: Constraint) -> tuple:
  A tuple of the SQLAlchemy ORM objects for the TAP_SCHEMA ``key``
  and ``key_columns`` data.
  """
- constraint_type = constraint_obj.type
  key = None
  key_columns = []
- if constraint_type == "ForeignKey":
+ if isinstance(constraint_obj, ForeignKeyConstraint):
  constraint_name = constraint_obj.name
  description = constraint_obj.description
  utype = constraint_obj.votable_utype