code: public boolean hasProperty(String category, String key) {
  		return this.categories.containsKey(category) && this.categories.get(category).containsKey(key);
  	}
docs: Checks whether the specified key is present in the specified category
  
  @param category The category to look into for the key
  @param key      The key to look for
  @return {@code true} if the key was found in the category, {@code false} otherwise