17. The at least one non-transitory computer-readable storage medium of claim 15 , wherein the method further comprises: modifying the second speech recognition model and the second NLU model based at least in part on the first data to obtain a third speech recognition model and a third NLU model, wherein the modifying comprises modifying the second speech recognition model and the second NLU model by using a second N-best list of word sequences generated by using the second speech recognition model to recognize at least the portion of the audio data.
15. At least one non-transitory computer-readable storage medium that stores processor-executable instructions that, when executed by at least one hardware processor, cause the at least one hardware processor to perform a method comprising: obtaining first data comprising audio data processed by a natural language understanding (NLU) system at least in part by using a first NLU model, a first N-best list of word sequences generated by using a first speech recognition model to recognize at least a portion of the audio data, and associated NLU data indicating how the audio data was understood by the NLU system; and modifying the first speech recognition model and the first NLU model based at least in part on the first data, including using the first N-best list of word sequences, to obtain a second speech recognition model and a second NLU model.