old_contents: import pytest
  
  from gaphor.diagram.tests.fixtures import allow, connect, disconnect
  from gaphor.SysML import sysml
  from gaphor.SysML.requirements.relationships import (
      DeriveReqtItem,
      RefineItem,
      SatisfyItem,
      TraceItem,
      VerifyItem,
  )
  from gaphor.SysML.requirements.requirement import RequirementItem
  
  
  @pytest.mark.parametrize(
      "item_class", [DeriveReqtItem, RefineItem, SatisfyItem, TraceItem, VerifyItem,]
  )
  def test_relation_allow_connect_disconnect_cycle(diagram, element_factory, item_class):
      req1 = element_factory.create(sysml.Requirement)
      req2 = element_factory.create(sysml.Requirement)
  
      req_item1 = diagram.create(RequirementItem, subject=req1)
      req_item2 = diagram.create(RequirementItem, subject=req2)
  
      relation = diagram.create(item_class)
  
      assert allow(relation, relation.handles()[0], req_item1)
      assert allow(relation, relation.handles()[1], req_item2)
  
      connect(relation, relation.handles()[0], req_item1)
      connect(relation, relation.handles()[1], req_item2)
  
      assert relation.subject
      assert relation.subject.sourceContext is req_item1.subject
      assert relation.subject.targetContext is req_item2.subject
  
      disconnect(relation, relation.handles()[0])
  
      assert not relation.subject
  
new_contents: import pytest
  
  from gaphor.diagram.tests.fixtures import allow, connect, disconnect
  from gaphor.SysML import sysml
  from gaphor.SysML.requirements.relationships import (
      DeriveReqtItem,
      RefineItem,
      SatisfyItem,
      TraceItem,
      VerifyItem,
  )
  from gaphor.SysML.requirements.requirement import RequirementItem
  
  
  @pytest.mark.parametrize(
      "item_class", [DeriveReqtItem, RefineItem, SatisfyItem, TraceItem, VerifyItem]
  )
  def test_relation_allow_connect_disconnect_cycle(diagram, element_factory, item_class):
      req1 = element_factory.create(sysml.Requirement)
      req2 = element_factory.create(sysml.Requirement)
  
      req_item1 = diagram.create(RequirementItem, subject=req1)
      req_item2 = diagram.create(RequirementItem, subject=req2)
  
      relation = diagram.create(item_class)
  
      assert allow(relation, relation.handles()[0], req_item1)
      assert allow(relation, relation.handles()[1], req_item2)
  
      connect(relation, relation.handles()[0], req_item1)
      connect(relation, relation.handles()[1], req_item2)
  
      assert relation.subject
      assert relation.subject.sourceContext is req_item1.subject
      assert relation.subject.targetContext is req_item2.subject
  
      disconnect(relation, relation.handles()[0])
  
      assert not relation.subject
  
subject: Fix flake8 error for missing whitespace