code: def list_concat(input, **params):
      
      PARAM_SOURCE_FIELDS = 'src.fields'
      PARAM_DEST_FIELD = 'dest.field'
  
      field_list = params.get(PARAM_SOURCE_FIELDS)
      for row in input:
          res = []
          for field in field_list:
              res += row[field]
          row[params.get(PARAM_DEST_FIELD)] = res
      return input
docs: Concatenates two or more lists and put result into dest field
      :param input:
      :param params:
      :return: