* 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`.

- CustomResourceDefinitions added support for marking versions as deprecated by setting `spec.versions[*].deprecated` to `true`, and for optionally overriding the default deprecation warning with a `spec.versions[*].deprecationWarning` field. ([#92329](https://github.com/kubernetes/kubernetes/pull/92329), [@liggitt](https://github.com/liggitt)) [SIG API Machinery]

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...

significant (trailing in little-endian) zero limbs. // We assume comparison with zero (but not the branch) is constant time. for i := len(x.limbs) - 1; i >= 0; i-- { if x.limbs[i] != 0 { break } x.limbs = x.limbs[:i] } return x } // set assigns x = y, optionally resizing x to the appropriate size. func (x *Nat) set(y *Nat) *Nat { x.reset(len(y.limbs)) copy(x.limbs, y.limbs) return x } // Bits returns x as a little-endian slice of uint. The length of the slice // matches the announced length of x. The result...

significant (trailing in little-endian) zero limbs. // We assume comparison with zero (but not the branch) is constant time. for i := len(x.limbs) - 1; i >= 0; i-- { if x.limbs[i] != 0 { break } x.limbs = x.limbs[:i] } return x } // set assigns x = y, optionally resizing x to the appropriate size. func (x *Nat) set(y *Nat) *Nat { x.reset(len(y.limbs)) copy(x.limbs, y.limbs) return x } // Bits returns x as a little-endian slice of uint. The length of the slice // matches the announced length of x. The result...