# CopyFilter **`class CopyFilter(config)`** Bases: [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) The copy [`Filter`](squirro.lib.nlp.steps.filters.Filter.md#squirro.lib.nlp.steps.filters.Filter) copies input fields into output fields with `copy.deepcopy` **Input** - No specific input fields type required as long as it is compatible with `copy.deepcopy` **Output** - The output field type is going to be the same as the input field type Parameters - `type` ([`str`](https://docs.python.org/3.11/library/stdtypes.html#str)) – copy - `input_fields` ([`list`](https://docs.python.org/3.11/library/stdtypes.html#list)) – Fields to copy - `output_fields` ([`list`](https://docs.python.org/3.11/library/stdtypes.html#list)) – Fields to copy into **Example** ```json { "step": "filter", "type": "copy", "input_fields":["body"], "output_fields":["copied_body"] } ``` 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)