src/Traits/HasParent.php
public function parentClass( $parentClass = 'undefined') {
    if( 'undefined' !== $parentClass ){
      if( ! is_object( $parentClass)){
        $this->exception('Invalid instance of a parent class.');
      } else {
        $this->traitHasParentClass = $parentClass;
      }
    }
    return $this->traitHasParentClass;
  }
public function parentClass( $parentClass = 'undefined') {
    if( 'undefined' !== $parentClass ){
      if( ! is_object( $parentClass)){
        $this->exception('Invalid instance of a parent class.');
      } else {
        $this->traitHasParentClass = $parentClass;
      }
    }
    return $this->traitHasParentClass;
  }
Parent class getter/setter

@param mixed $parentClass Parent class instance
@return mixed Parent class