Secondary notation provides redundant (more than necessary) information; if the visual cues are the only way that some information is provided, such as in traffic lights, or a chart's key, it is not secondary. Secondary notation is often not a part of the formal notation itself. Rather, it is a method of organizing the formal notation to allow it to be more easily understood. Thus, secondary notation does not change the actual meaning of the formal notation, rather it allows for the meaning to be readily understood. In text such as programming languages, this can be done using cues such as indentation and coloring. In formal graphical notations, this can be done through the use of symmetry or proximity to indicate relatedness.