old_contents: from __future__ import absolute_import
  
  from .req_install import InstallRequirement
  from .req_set import RequirementSet, Requirements
  from .req_file import parse_requirements
  
  __all__ = [
      RequirementSet, Requirements, InstallRequirement, parse_requirements,
  ]
  
new_contents: from __future__ import absolute_import
  
  from .req_install import InstallRequirement
  from .req_set import RequirementSet, Requirements
  from .req_file import parse_requirements
  
  __all__ = [
      "RequirementSet", "Requirements", "InstallRequirement",
      "parse_requirements",
  ]
  
subject: Fix req.__all__.