code: function(publicKey, privateKey, callback) {
          if (!publicKey || !privateKey) {
              throw new Error('Both public key and private key must be specified');
          }
  
          var url = this.getResourceUrl({ path: '/keys/' + publicKey, user: null });
          request({
              method: 'PUT',
              uri: this.getSignedResourceUrl('PUT', url),
              json: { privateKey: privateKey },
              onComplete: callback
          });
  
          return this;
      }
docs: Edit a public/private key pair
  
  @param {String} publicKey Public key you want to edit
  @param {String} privateKey Private key for the public key
  @param {Function} callback
  @return {ImboClient}