Seq2SeqLM

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Seq2SeqLM class

keras_nlp.models.Seq2SeqLM()

Base class for sequence to sequence language modeling tasks.

Seq2SeqLM tasks wrap a keras_hub.models.Backbone and a keras_hub.models.Preprocessor to create a model that can be used for generation and generative fine-tuning, when generation is conditioned on additional input sequence in a sequence-to-sequence setting.

Seq2SeqLM tasks provide an additional, high-level generate() function which can be used to auto-regressively sample an output sequence token by token. The compile() method of Seq2SeqLM classes contains an additional sampler argument, which can be used to pass a keras_hub.samplers.Sampler to control how the predicted distribution will be sampled.

When calling fit(), each input should contain an input and output sequence. The model will be trained to predict the output sequence token-by-token using a causal mask, similar to a keras_hub.models.CausalLM task. Unlike the CausalLM task, an input sequence must be passed, and can be attended to in full by all tokens in the output sequence.

All Seq2SeqLM tasks include a from_preset() constructor which can be used to load a pre-trained config and weights.

Example

# Load a Bart backbone with pre-trained weights.
seq_2_seq_lm = keras_hub.models.Seq2SeqLM.from_preset(
    "bart_base_en",
)
seq_2_seq_lm.compile(sampler="top_k")
# Generate conditioned on the `"The quick brown fox."` as an input sequence.
seq_2_seq_lm.generate("The quick brown fox.", max_length=30)

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from_preset method

Seq2SeqLM.from_preset(preset, load_weights=True, **kwargs)

Instantiate a keras_hub.models.Task from a model preset.

A preset is a directory of configs, weights and other file assets used to save and load a pre-trained model. The preset can be passed as one of:

1. a built-in preset identifier like 'bert_base_en'
2. a Kaggle Models handle like 'kaggle://user/bert/keras/bert_base_en'
3. a Hugging Face handle like 'hf://user/bert_base_en'
4. a path to a local preset directory like './bert_base_en'

For any Task subclass, you can run cls.presets.keys() to list all built-in presets available on the class.

This constructor can be called in one of two ways. Either from a task specific base class like keras_hub.models.CausalLM.from_preset(), or from a model class like keras_hub.models.BertTextClassifier.from_preset(). If calling from the a base class, the subclass of the returning object will be inferred from the config in the preset directory.

Arguments

• preset: string. A built-in preset identifier, a Kaggle Models handle, a Hugging Face handle, or a path to a local directory.
• load_weights: bool. If True, saved weights will be loaded into the model architecture. If False, all weights will be randomly initialized.

Examples

# Load a Gemma generative task.
causal_lm = keras_hub.models.CausalLM.from_preset(
    "gemma_2b_en",
)

# Load a Bert classification task.
model = keras_hub.models.TextClassifier.from_preset(
    "bert_base_en",
    num_classes=2,
)

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compile method

Seq2SeqLM.compile(
    optimizer="auto", loss="auto", weighted_metrics="auto", sampler="top_k", **kwargs
)

Configures the CausalLM task for training and generation.

The CausalLM task extends the default compilation signature of keras.Model.compile with defaults for optimizer, loss, and weighted_metrics. To override these defaults, pass any value to these arguments during compilation.

The CausalLM task adds a new sampler to compile, which can be used to control the sampling strategy used with the generate function.

Note that because training inputs include padded tokens which are excluded from the loss, it is almost always a good idea to compile with weighted_metrics and not metrics.

Arguments

• optimizer: "auto", an optimizer name, or a keras.Optimizer instance. Defaults to "auto", which uses the default optimizer for the given model and task. See keras.Model.compile and keras.optimizers for more info on possible optimizer values.
• loss: "auto", a loss name, or a keras.losses.Loss instance. Defaults to "auto", where a keras.losses.SparseCategoricalCrossentropy loss will be applied for the token classification CausalLM task. See keras.Model.compile and keras.losses for more info on possible loss values.
• weighted_metrics: "auto", or a list of metrics to be evaluated by the model during training and testing. Defaults to "auto", where a keras.metrics.SparseCategoricalAccuracy will be applied to track the accuracy of the model at guessing masked token values. See keras.Model.compile and keras.metrics for more info on possible weighted_metrics values.
• sampler: A sampler name, or a keras_hub.samplers.Sampler instance. Configures the sampling method used during generate() calls. See keras_hub.samplers for a full list of built-in sampling strategies.
• **kwargs: See keras.Model.compile for a full list of arguments supported by the compile method.

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generate method

Seq2SeqLM.generate(
    inputs, max_length=None, stop_token_ids="auto", strip_prompt=False
)

Generate text given prompt inputs.

This method generates text based on given inputs. The sampling method used for generation can be set via the compile() method.

If inputs are a tf.data.Dataset, outputs will be generated "batch-by-batch" and concatenated. Otherwise, all inputs will be handled as a single batch.

If a preprocessor is attached to the model, inputs will be preprocessed inside the generate() function and should match the structure expected by the preprocessor layer (usually raw strings). If a preprocessor is not attached, inputs should match the structure expected by the backbone. See the example usage above for a demonstration of each.

Arguments

• inputs: python data, tensor data, or a tf.data.Dataset. If a preprocessor is attached to the model, inputs should match the structure expected by the preprocessor layer. If a preprocessor is not attached, inputs should match the structure expected the backbone model.
• max_length: Optional. int. The max length of the generated sequence. Will default to the max configured sequence_length of the preprocessor. If preprocessor is None, inputs should be should be padded to the desired maximum length and this argument will be ignored.
• stop_token_ids: Optional. None, "auto", or tuple of token ids. Defaults to "auto" which uses the preprocessor.tokenizer.end_token_id. Not specifying a processor will produce an error. None stops generation after generating max_length tokens. You may also specify a list of token id's the model should stop on. Note that sequences of tokens will each be interpreted as a stop token, multi-token stop sequences are not supported.
• strip_prompt: Optional. By default, generate() returns the full prompt followed by its completion generated by the model. If this option is set to True, only the newly generated text is returned.

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save_to_preset method

Seq2SeqLM.save_to_preset(preset_dir)

Save task to a preset directory.

Arguments

• preset_dir: The path to the local model preset directory.

preprocessor property

keras_nlp.models.Seq2SeqLM.preprocessor

A keras_hub.models.Preprocessor layer used to preprocess input.

backbone property

keras_nlp.models.Seq2SeqLM.backbone

A keras_hub.models.Backbone model with the core architecture.