code: async function verifyDevice (userId, deviceId) {
      await exports.matrixClient.setDeviceKnown(userId, deviceId, true);
      await exports.matrixClient.setDeviceVerified(userId, deviceId, true);
  }
docs: This function calls the functions from matrix-js-sdk to verify
  the devices.
  Implicitly returns a Promise because it's an async function.
  
  @function verifyDevice
  
  @param userId - The user who's devices has to be verified
  @param deviceId - The ID of the device which has to be verified
  @returns {Promise<void>}