code: function (key) {
          var lastDisabledVariable;
  
          this.values.remove(function (variable) {
              // bail out if variable name didn't match
              if (variable.key !== key) {
                  return false;
              }
  
              // don't delete disabled variables
              if (variable.disabled) {
                  lastDisabledVariable = variable;
                  return false;
              }
  
              // delete all enabled variables
              return true;
          });
  
          // restore the reference with the last disabled variable
          if (lastDisabledVariable) {
              this.values.reference[key] = lastDisabledVariable;
          }
  
          // track the change if mutation tracking is enabled
          this._postman_enableTracking && this.mutations.track(MUTATIONS.UNSET, key);
      }
docs: Removes the variable with the specified name.
  
  @param {String} key