code: function API(opts) {
    opts = opts || {};
  
    this.request = opts.request || request;
    this.baseUrl = opts.baseUrl || BASE_URL;
    this.payProHttp = null; // Only for testing
    this.doNotVerifyPayPro = opts.doNotVerifyPayPro;
    this.timeout = opts.timeout || 50000;
    this.logLevel = opts.logLevel || 'silent';
    this.supportStaffWalletId = opts.supportStaffWalletId;
  
    log.setLevel(this.logLevel);
  }
docs: @desc ClientAPI constructor.
  
  @param {Object} opts
  @constructor