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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def subsystem_dependencies_iter(cls):
 """Iterate over the direct subsystem dependencies of this Optionable."""

    for dep in cls.subsystem_dependencies():
      if isinstance(dep, SubsystemDependency):
        yield dep
      else:
        yield SubsystemDependency(dep, GLOBAL_SCOPE, removal_version=None, removal_hint=None)