def my_cancel_child_order(product_code:, child_order_id: nil, child_order_acceptance_id: nil)
      return unless child_order_id || child_order_acceptance_id

      body =
        if child_order_id
          "{
            'product_code': \"#{product_code}\",
            'child_order_id': \"#{child_order_id}\"
          }"
        elsif child_order_acceptance_id
          "{
            'product_code': \"#{product_code}\",
            'child_order_acceptance_id': \"#{child_order_acceptance_id}\"
          }"
        end

      res = conn.post do |req|
        req.url "/v1/me/cancelchildorder"
        req.body = body
      end

      res.body
    end
def my_cancel_child_order(product_code:, child_order_id: nil, child_order_acceptance_id: nil)
      return unless child_order_id || child_order_acceptance_id

      body =
        if child_order_id
          "{
            'product_code': \"#{product_code}\",
            'child_order_id': \"#{child_order_id}\"
          }"
        elsif child_order_acceptance_id
          "{
            'product_code': \"#{product_code}\",
            'child_order_acceptance_id': \"#{child_order_acceptance_id}\"
          }"
        end

      res = conn.post do |req|
        req.url "/v1/me/cancelchildorder"
        req.body = body
      end

      res.body
    end
TODO: merge child_order_id and child_order_acceptance_id