fix-variables-performance-9c90a58c968aa710.yaml

---
features:
  - |
    Improve the performance of ``ConstrainedQuadraticModel.fix_variable()`` and
    ``ConstrainedQuadraticModel.fix_variables()``.
  - |
    Add ``inplace`` keyword argument to ``ConstrainedQuadraticModel.fix_variables()``.
upgrade:
  - |
    The ``ConstrainedQuadraticModel.fix_variables()`` function now returns
    a ``ConstrainedQuadraticModel`` rather than an empty dictionary.