if (!ThroughWLModel.attributes[attrDef.via]) {
          throw new Error('Consistency violation: The referenced attribute (`'+attrName+'`, from model `'+modelIdentity+'`) is a "through" association, because it declares a `through`.  But the association\'s specified `via` ('+attrDef.via+'`) does not correspond with a recognized attribute on the junction model (`'+attrDef.through+'`)');
        }