* Add support for type annotations using `Optional` as in `param: Optional[str] = None`. New documentation: [Optional type declarations](https://fastapi.tiangolo.com/tutorial/query-params/#optional-type-declarations).
    * PR [#278](https://github.com/tiangolo/fastapi/pull/278).

## 0.26.0

### Bug Fixes and Other Changes

* `tf.data`
    * Add optional `synchronous` argument to `map`, to specify that the `map` should run synchronously, as opposed to be parallelizable when `options.experimental_optimization.map_parallelization=True`. This saves memory compared to setting `num_parallel_calls=1`.

- Fix a concurrent map writes error in kubelet ([#93773](https://github.com/kubernetes/kubernetes/pull/93773), [@knight42](https://github.com/knight42)) [SIG Node]
- Fix a regression where kubeadm bails out with a fatal error when an optional version command line argument is supplied to the "kubeadm upgrade plan" command ([#94421](https://github.com/kubernetes/kubernetes/pull/94421), [@rosti](https://github.com/rosti)) [SIG Cluster Lifecycle]

auto;\n\n    // Bring the hover, focused, and \"active\" buttons to the front to overlay\n    // the borders properly\n    @include hover() {\n      z-index: 1;\n    }\n    &:focus,\n    &:active,\n    &.active {\n      z-index: 1;\n    }\n  }\n}\n\n// Optional: Group multiple button groups together for a toolbar\n.btn-toolbar {\n  display: flex;\n  flex-wrap: wrap;\n  justify-content: flex-start;\n\n  .input-group {\n    width: auto;\n  }\n}\n\n.btn-group {\n  // Prevent double borders when buttons are...

focused, and \"active\" buttons to the front to overlay\n  // the borders properly\n  > .btn-check:checked + .btn,\n  > .btn-check:focus + .btn,\n  > .btn:hover,\n  > .btn:focus,\n  > .btn:active,\n  > .btn.active {\n    z-index: 1;\n  }\n}\n\n// Optional: Group multiple button groups together for a toolbar\n.btn-toolbar {\n  display: flex;\n  flex-wrap: wrap;\n  justify-content: flex-start;\n\n  .input-group {\n    width: auto;\n  }\n}\n\n.btn-group {\n  @include border-radius($btn-border-radius);\n\n...

err != nil { return nil, err } // See https://github.com/cfrg/draft-irtf-cfrg-det-sigs-with-noise/issues/6 // for the FIPS compliance of this method. In short Z is entropy from the // main DRBG, of length 3/2 of security_strength, so the nonce is optional // per SP 800-90Ar1, Section 8.6.7, and the rest is a personalization // string, which per SP 800-90Ar1, Section 8.7.1 may contain secret // information. drbg := newDRBG(h, Z, nil, blockAlignedPersonal{priv.d, bits2octets(c, hash)}) return sign(c,...