# SemanticTermExpander **`class SemanticTermExpander(config)`** Bases: [`BatchedStep`](../technical/libnlp/steps/standard.md#squirro.lib.nlp.steps.batched_step.BatchedStep) Find and add synonyms dynamically via (domain-specific) language models. Provide pretrained models per language via: - path to file-system - or pretrained models available from gensim-data [RaRe-Technologies/gensim-data](https://github.com/RaRe-Technologies/gensim-data) Example usage: - Input query: why is austria again the virus center - Output term expansion mutations: ```json { "austria": "( austria OR germany^0.86 OR switzerland^0.86 )", "virus": "( virus OR h5n1^0.88 OR flu^0.88 )", "center": "( center OR centers^0.8 OR centre^0.78 )" } ``` Annotated mutation dictionary can be used in a following step. Parameters - `step` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``"app"`) – app - `type` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``"query_processing"`) – query_processing - `name` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``"semantic_term_expander"`) – semantic_term_expander - `analyzed_input_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``"nlp"`) – analyzed spacy Doc - `output_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``"term_expansion_mutations"`) – the modified query string - `model_mapping` ([`dict`](https://docs.python.org/3.11/library/stdtypes.html#dict)) – mapping from language code to semantic-model-path to load - `expand_by_pos` ([`list`](https://docs.python.org/3.11/library/stdtypes.html#list)`, ``[``"NOUN"``,``"PROPN"``]`) – list of POS tags that are used to expand query term - `max_expansions` ([`int`](https://docs.python.org/3.11/library/functions.html#int)`, ``3`) – how many single tokens should be used for expansions - `expansions_per_term` ([`int`](https://docs.python.org/3.11/library/functions.html#int)`, ``2`) – how many similar terms are added to a selected token (for expansion) - `similarity_threshold` ([`float`](https://docs.python.org/3.11/library/functions.html#float)`, ``0.5`) – minimum similarity of user-token to model-token to be used for expansion - `path` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``"."`) – path Methods SummaryMethods Documentation **`get_expand_candidates(analyzed_query)`** Currently only apply semantic term expansion on single term tokens // and selected POS type. **`process_doc(doc)`** Process a document Parameters `doc` ([`Document`](../technical/libnlp/base.md#squirro.lib.nlp.document.Document)) – Document Returns Processed document Return type [Document](../technical/libnlp/base.md#squirro.lib.nlp.document.Document)