def op_type(params = {})
      if es_version_5_x? && (params.key?(:_op_type) || params.key?("_op_type"))
        params[:op_type] = params.delete(:_op_type)
      end
      params
    end
def op_type(params = {})
      if es_version_5_x? && (params.key?(:_op_type) || params.key?("_op_type"))
        params[:op_type] = params.delete(:_op_type)
      end
      params
    end
COMPATIBILITY: handle _op_type -> op_type request param conversion for put-if-absent bnehavior
 Returns the (possibly mutated) params hash supplied by the caller.

 https://www.elastic.co/guide/en/elasticsearch/reference/current/docs-index_.html#operation-type