old_contents: from .model_checker import ModelChecker, PathResult, PathMetric
  from .pysb import PysbModelChecker
  from .signed_graph import SignedGraphModelChecker
  from .unsigned_graph import UnsignedGraphModelChecker
  from .pybel import PybelModelChecker
  
new_contents: from .model_checker import ModelChecker, PathResult, PathMetric, get_path_iter
  from .pysb import PysbModelChecker
  from .signed_graph import SignedGraphModelChecker
  from .unsigned_graph import UnsignedGraphModelChecker
  from .pybel import PybelModelChecker
  
subject: Add get_path_iter to model_checker importables