function isEncryptedValue(object, property) {
  const value = object[property];
  assert.ok(isBsonType(value, 'Binary'), `auto encryption for property ${property} failed: not a BSON binary.`);
  assert.ok(value.sub_type === 6, `auto encryption for property ${property} failed: not subtype 6.`);
}
@param {object} object
@param {string} property