Make a public API request
function (command, parameters, callback) {
      if (typeof parameters === 'function') {
        callback = parameters;
        parameters = {};
      }

      parameters || (parameters = {});
      parameters.command = command;
      
      const options = {
        method: 'GET',
        url: PUBLIC_API_URL,
        qs: parameters
      };

      options.qs.command = command;

      return this._request(options, callback);
    }