public function get_fields()
    {
        if( !isset( $this->fields ) )
        {
            if( !$this->has_sub_sections() )
            {
                $this->fields = $this->model['fields'];
            }
            else
            {
                $this->fields = array();
                foreach( $this->model['subsections'] as $subsection )
                {
                    foreach( $subsection['fields'] as $field )
                    {
                        $field->subsection = \Amarkal\Common\Tools::strtoslug( $subsection['title'] );
                    }
                    $this->fields = array_merge( $this->fields, $subsection['fields'] );
                }
            }
        }
        return $this->fields;
    }