Get the SUM of Two COUNTS in Sequelize

Question

Is there a way to add/sum two attribute COUNT functions with sequelize? I want to get the sum of impMeta1Count and impMeta2Count.

imp.findAll({
  attributes: {
    include: [
      [Sequelize.fn("COUNT", Sequelize.col('meta1.impId')), 'impMeta1Count'],
      [Sequelize.fn("COUNT", Sequelize.col('meta3.impId')), 'impMeta2Count']
    ]
  },
  include: [
    { model: meta1, attributes: [], required: false },
    { model: meta2, attributes: [], required: false }
  ],
  group: ['imp.id']
})