code: function validate (uri, collection, cb) {
    if ('function' != typeof cb) {
      throw new TypeError('cb must be a function');
    }
  
    if ('string' != typeof collection) {
      throw new TypeError('collection must be a string');
    }
  
    if ('string' != typeof uri) {
      throw new TypeError('uri must be a string');
    }
  }
docs: validate "miner" arguments