docs: def _get_pk_from_identity(obj):
          """Copied / pasted, and fixed, from WTForms_sqlalchemy due to issue w/
          SQLAlchemy >= 1.2."""
          from sqlalchemy.orm.util import identity_key
  
          cls, key = identity_key(instance=obj)[0:2]
          return ":".join(text_type(x) for x in key)