Also migrates a handful of usage sites as necessary, and
moves all users of `is_tuple` and co. to `is_struct`.

PiperOrigin-RevId: 322865881

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-  Migrate the train dataset preprocessing function into the iterative process,
   rather than part of dataset building the client data function. This is necessary
   to enable serialization of datasets for sending to remote workers.

PiperOrigin-RevId: 322691112

Additionally, introduces a simple ABC that FederatedComputationContext subclasses, to expose interface encoding attributes previously added to FederatedComputationContext.

PiperOrigin-RevId: 322690886

In particular, ensures computations never mask names from their parent scopes which are referenced in their bodies.

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This should allow us to actually guarantee transformation to call-dominant form succeeds, that we can simply rely on intrinsic pattern-matching to pull called intrinsics out to the top-level let statement.

PiperOrigin-RevId: 322601696

This change moves and renames `AnonymousTuple` and its `Type`-based
brethren. It re-exports the new types under the old names to allow
for a more gradual transition to the new API.

PiperOrigin-RevId: 322477504

PiperOrigin-RevId: 322458614

The dataset returns only a single element and cannot be unpacked.

PiperOrigin-RevId: 322454423

This will require changing both the model and the model wrapper.

PiperOrigin-RevId: 322443809

PiperOrigin-RevId: 322436602

PiperOrigin-RevId: 322430991

Update Text Generation tutorial to reflect changes in preservation of Python containers across all of TFF.

Additionally:
- Use more efficient concatenated dataset construction.
- Reduce memory usage by using only two clients and a smaller shuffle buffer in the example.
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PiperOrigin-RevId: 322407034

This change introduces a transformation which guarantees that any instances of a `Call` building block in its return value are either to a concrete function, or a call to a function accepted as a parameter to an uncalled function.

By setting up this invariant, complexity in other transformations can be significantly reduced.

PiperOrigin-RevId: 322402665

`tf.data.Dataset` cannot yield `AnonymousTuple`, so it must have been
constructed by TFF with an appropriate Python container already, so we don't
need to do anything.

PiperOrigin-RevId: 322402388

PiperOrigin-RevId: 322400322

Binds references to remaining call construction sites in `ValueImpl`, cleans up tests depending on old behavior.

PiperOrigin-RevId: 322394328

Fix error-checking logic for `get_canonical_form_for_iterative_process()` for `IterativeProcess`'s with no aggregation.

The logic was previously failing for this case, but with a harder to grok error message.

The previous logic had a slight bug in the branching logic, such that we would never hit the explicit `ValueError` in the final `else:` block.

The tests were also incorrectly passing because they hit a different validation check:

```
ValueError: Expected an AST containing an intrinsic with the uri: federated_secure_sum, found none.
```
PiperOrigin-RevId: 322385240

PiperOrigin-RevId: 322377616

Also while were here, update to some more modern TFF coding practices:
-  Use `tff.learning.framework.ModelWeights` instead of a custom type.
-  Delete `from_tff_result` conversion helper, it is no longer needed.
-  Remove unused test helper methods.
-  Replace numpy dependency with TF ops.

PiperOrigin-RevId: 322359152

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This is a pattern we have used frequently (e.g. in ReferenceResolvingExecutor's evaluate method) to persist more  information in traces.

Currently a little difficult to narrow down hotspots in serialization code.

Additionally adds PyType annotations and cleans up the contracts a little bit, easier with this new factorization.

PiperOrigin-RevId: 322246977

This will preserve the returned container value, making it usable with utilities such as `tf.nest`.

PiperOrigin-RevId: 322236441

- Remove use of `tff.NamedTupleType` and use Python containers and avoid
  exposing AnonymousTuple.
- Add handling of `tff.SequenceType` to type conversion code.
- Change ReferenceExecutor to convert values unconditionally.

PiperOrigin-RevId: 322232543

PiperOrigin-RevId: 322178848

Previously, NamedTupleTypeWithPyContainerType was often lost and turned into
a NamedTupleType without the container. This resulted in users being given
AnonymousTuples when a more specific container should have been returned.

This change fixes a large number of sites where container types were lost, and
adjusts usage sites as appropriate, including the removal of `from_tff_result`
functions.

This change also makes the `__eq__` function for
`NamedTupleTypeWithPyContainerType` require equivalent container types, rather
than just equivalent field structure. Call sites that wished to compare only
field structure are adjusted to use `Type.{is, check}_equivalent_to`.

PiperOrigin-RevId: 321883012

PiperOrigin-RevId: 321852405

stackoverflow so it can be passed to the iterative process.

Make shuffling conidition on the buffer size.

PiperOrigin-RevId: 321846124

Extend iterative process builder and the LR scheduling iterative process to accept an optional"datasset preprocessing computation.

This allows for pushing the dataset preprocessing methods down to the client
executors, which is required for multimachine simulations since stateful
datasets (e.g. datasets which suffling) cannot be serialized.

PiperOrigin-RevId: 321835968