code: function assignSetterFnForNode( handler, node ) {
  	let setterFn;
  
  	// For each node, add its handler to the relevant "level" representation
  	addLevelOption( handler._levels, node.level, {
  		component: node.component,
  		validate: node.validate,
  		methods: node.methods,
  	} );
  
  	// First level is set implicitly, no dedicated setter needed
  	if ( node.level > 0 ) {
  
  		setterFn = createPathPartSetter( node );
  
  		node.names.forEach( ( name ) => {
  			// Convert from snake_case to camelCase
  			const setterFnName = name.replace(
  				/[_-]+\w/g,
  				match => match.replace( /[_-]+/, '' ).toUpperCase()
  			);
  
  			// Don't overwrite previously-set methods
  			if ( ! handler._setters[ setterFnName ] ) {
  				handler._setters[ setterFnName ] = setterFn;
  			}
  		} );
  	}
  }
docs: Assign a setter function for the provided node to the provided route
  handler object setters dictionary (mutates handler by reference).
  
  @private
  @param {Object} handler A route handler definition object
  @param {Object} node    A route hierarchy level node object