# MergeFilter **`class MergeFilter(config)`** Bases: [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) The merge [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) merges multiple fields into a single field **Input** - all input fields needs to be of type [`str`](https://docs.python.org/3.11/library/stdtypes.html#str), [`list`](https://docs.python.org/3.11/library/stdtypes.html#list) [ [`str`](https://docs.python.org/3.11/library/stdtypes.html#str) ] or [`list`](https://docs.python.org/3.11/library/stdtypes.html#list) [ {‘body’: [`str`](https://docs.python.org/3.11/library/stdtypes.html#str)} ]. **Output** - the output field is filled with data of type [`str`](https://docs.python.org/3.11/library/stdtypes.html#str). Parameters - `type` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)) – merge - `input_fields` ([`list`](https://docs.python.org/3.11/library/stdtypes.html#list)) – Fields to merge - `output_field` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)) – Field to merge into - `delimiter` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)`, ``' '`) – String to merge on **Example** ```json { "step": "filter", "type": "merge", "input_fields":["title","body"], "output_field":"text" } ``` Methods SummaryMethods Documentation **`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)