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class SimpleTagger(Model):
 | def __init__(
 |     self,
 |     vocab: Vocabulary,
 |     text_field_embedder: TextFieldEmbedder,
 |     encoder: Seq2SeqEncoder,
 |     calculate_span_f1: bool = None,
 |     label_encoding: Optional[str] = None,
 |     label_namespace: str = "labels",
 |     verbose_metrics: bool = False,
 |     initializer: InitializerApplicator = InitializerApplicator(),
 |     **kwargs
 | ) -> None

This SimpleTagger simply encodes a sequence of text with a stacked Seq2SeqEncoder, then predicts a tag for each token in the sequence.

Registered as a Model with name "simple_tagger".


  • vocab : Vocabulary
    A Vocabulary, required in order to compute sizes for input/output projections.
  • text_field_embedder : TextFieldEmbedder
    Used to embed the tokens TextField we get as input to the model.
  • encoder : Seq2SeqEncoder
    The encoder (with its own internal stacking) that we will use in between embedding tokens and predicting output tags.
  • calculate_span_f1 : bool, optional (default = None)
    Calculate span-level F1 metrics during training. If this is True, then label_encoding is required. If None and label_encoding is specified, this is set to True. If None and label_encoding is not specified, it defaults to False.
  • label_encoding : str, optional (default = None)
    Label encoding to use when calculating span f1. Valid options are "BIO", "BIOUL", "IOB1", "BMES". Required if calculate_span_f1 is true.
  • label_namespace : str, optional (default = labels)
    This is needed to compute the SpanBasedF1Measure metric, if desired. Unless you did something unusual, the default value should be what you want.
  • verbose_metrics : bool, optional (default = False)
    If true, metrics will be returned per label class in addition to the overall statistics.
  • initializer : InitializerApplicator, optional (default = InitializerApplicator())
    Used to initialize the model parameters.


class SimpleTagger(Model):
 | ...
 | def forward(
 |     self,
 |     tokens: TextFieldTensors,
 |     tags: torch.LongTensor = None,
 |     metadata: List[Dict[str, Any]] = None,
 |     ignore_loss_on_o_tags: bool = False
 | ) -> Dict[str, torch.Tensor]


  • tokens : TextFieldTensors
    The output of TextField.as_array(), which should typically be passed directly to a TextFieldEmbedder. This output is a dictionary mapping keys to TokenIndexer tensors. At its most basic, using a SingleIdTokenIndexer this is : {"tokens": Tensor(batch_size, num_tokens)}. This dictionary will have the same keys as were used for the TokenIndexers when you created the TextField representing your sequence. The dictionary is designed to be passed directly to a TextFieldEmbedder, which knows how to combine different word representations into a single vector per token in your input.
  • tags : torch.LongTensor, optional (default = None)
    A torch tensor representing the sequence of integer gold class labels of shape (batch_size, num_tokens).
  • metadata : List[Dict[str, Any]], optional (default = None)
    metadata containing the original words in the sentence to be tagged under a 'words' key.
  • ignore_loss_on_o_tags : bool, optional (default = False)
    If True, we compute the loss only for actual spans in tags, and not on O tokens. This is useful for computing gradients of the loss on a single span, for interpretation / attacking.


  • An output dictionary consisting of:
    • logits (torch.FloatTensor) : A tensor of shape (batch_size, num_tokens, tag_vocab_size) representing unnormalised log probabilities of the tag classes.
    • class_probabilities (torch.FloatTensor) : A tensor of shape (batch_size, num_tokens, tag_vocab_size) representing a distribution of the tag classes per word.
    • loss (torch.FloatTensor, optional) : A scalar loss to be optimised.


class SimpleTagger(Model):
 | ...
 | def make_output_human_readable(
 |     self,
 |     output_dict: Dict[str, torch.Tensor]
 | ) -> Dict[str, torch.Tensor]

Does a simple position-wise argmax over each token, converts indices to string labels, and adds a "tags" key to the dictionary with the result.


class SimpleTagger(Model):
 | ...
 | def get_metrics(self, reset: bool = False) -> Dict[str, float]


class SimpleTagger(Model):
 | ...
 | default_predictor = "sentence_tagger"