$declarations = $this->css_rules[ $selector ]->get_declarations();

			foreach ( $duplicates as $key ) {
				// Unset the duplicates from the $selectors_json array to avoid looping through them as well.
				unset( $selectors_json[ $key ] );
				// Remove the rules from the rules collection.
				unset( $this->css_rules[ $key ] );
			}
			// Create a new rule with the combined selectors.
			$duplicate_selectors                     = implode( ',', $duplicates );
			$this->css_rules[ $duplicate_selectors ] = new WP_Style_Engine_CSS_Rule( $duplicate_selectors, $declarations );
		}
	}
}