code: function list(category){
  	let list = [];
  
  	if (category && typeof(category) === 'string') {
  		list = _(goblin.ambush).filter(function(current) {
  			return _.includes(current.category, category);
  		}).map('id').value();
  	} else {
  		list = _(goblin.ambush).map('id').value();
  	}
  	
  	return list;
  
  }
docs: List all ambush function ids that match the passed category. If actegory is a falsy
  then all ambush functions will be listed.
  
  @param {string} category Ambush function category.
  @returns {array} Ids of the ambush functions of that category.