Constrained Beam Search [without disjunctive decoding] (#15416)

* added classes to get started with constrained beam search

* in progress, think i can directly force tokens now but not yet with the round robin

* think now i have total control, now need to code the bank selection

* technically works as desired, need to optimize and fix design choices leading to undersirable outputs

* complete PR #1 without disjunctive decoding

* removed incorrect tests

* Delete k.txt

* Delete test.py

* Delete test.sh

* revert changes to test scripts

* genutils

* full implementation with testing, no disjunctive yet

* shifted docs

* passing all tests realistically ran locally

* removing accidentally included print statements

* fixed source of error in initial PR test

* fixing the get_device() vs device trap

* fixed documentation docstrings about constrained_beam_search

* fixed tests having failing for Speech2TextModel's floating point inputs

* fix cuda long tensor

* added examples and testing for them and founx & fixed a bug in beam_search and constrained_beam_search

* deleted accidentally added test halting code with assert False

* code reformat

* Update tests/test_generation_utils.py

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* Update tests/test_generation_utils.py

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* Update tests/test_generation_utils.py

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* Update tests/test_generation_utils.py

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

* Update tests/test_generation_utils.py

* fixing based on comments on PR

* took out the testing code that should but work fails without the beam search moditification ; style changes

* fixing comments issues

* docstrings for ConstraintListState

* typo in PhrsalConstraint docstring

* docstrings improvements

Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

docs/source/internal/generation_utils.mdx

@@ -16,8 +16,9 @@ This page lists all the utility functions used by [`~generation_utils.Generation
 [`~generation_utils.GenerationMixin.greedy_search`],
 [`~generation_utils.GenerationMixin.sample`],
 [`~generation_utils.GenerationMixin.beam_search`],
-[`~generation_utils.GenerationMixin.beam_sample`], and
-[`~generation_utils.GenerationMixin.group_beam_search`].
+[`~generation_utils.GenerationMixin.beam_sample`],
+[`~generation_utils.GenerationMixin.group_beam_search`], and
+[`~generation_utils.GenerationMixin.constrained_beam_search`].
 
 Most of those are only useful if you are studying the code of the generate methods in the library.
 
@@ -190,6 +191,16 @@ A [`StoppingCriteria`] can be used to change when to stop generation (other than
 [[autodoc]] MaxTimeCriteria
     - __call__
 
+## Constraints
+
+A [`Constraint`] can be used to force the generation to include specific tokens or sequences in the output.
+
+[[autodoc]] Constraint
+
+[[autodoc]] PhrasalConstraint
+
+[[autodoc]] ConstraintListState
+
 ## BeamSearch
 
 [[autodoc]] BeamScorer
@@ -200,6 +211,10 @@ A [`StoppingCriteria`] can be used to change when to stop generation (other than
     - process
     - finalize
 
+[[autodoc]] ConstrainedBeamSearchScorer
+    - process
+    - finalize
+
 ## Utilities
 
 [[autodoc]] top_k_top_p_filtering