text: ---
  upgrade:
    - |
      A new requirement has been added to the requirements list,
      `retworkx <https://pypi.org/project/retworkx/>`_. It is an Apache 2.0
      licensed graph library that has a similar API to networkx and is being used
      to significantly speed up the :class:`qiskit.dagcircuit.DAGCircuit`
      operations as part of the transpiler. There are binaries published on PyPI
      for all the platforms supported by Qiskit Terra but if you're using a
      platform where there aren't precompiled binaries published refer to the
      `retworkx documentation
      <https://retworkx.readthedocs.io/en/stable/README.html#installing-retworkx>`_
      for instructions on pip installing from sdist.
  
      If you encounter any issues with the transpiler or DAGCircuit class as part
      of the transition you can switch back to the previous networkx
      implementation by setting the environment variable ``USE_RETWORKX`` to
      ``N``. This option will be removed in the 0.14.0 release.
  