code: protected function validateCondition($condition)
      {
          if (!is_array($condition)) {
              $this->addError($this->filterAttributeName, $this->parseErrorMessage('invalidFilter'));
              return;
          }
  
          if (empty($condition)) {
              return;
          }
  
          foreach ($condition as $key => $value) {
              $method = 'validateAttributeCondition';
              if (isset($this->filterControls[$key])) {
                  $controlKey = $this->filterControls[$key];
                  if (isset($this->conditionValidators[$controlKey])) {
                      $method = $this->conditionValidators[$controlKey];
                  }
              }
              $this->$method($key, $value);
          }
      }
docs: Validates filter condition.
  @param mixed $condition raw filter condition.