The boxes represent the objects (classes) that make up PyEvolve

<p><b>Copyright information:</b></p><p>Taken from "PyEvolve: a toolkit for statistical modelling of molecular evolution"</p><p>BMC Bioinformatics 2004;5():1-1.</p><p>Published online 5 Jan 2004</p><p>PMCID:PMC317364.</p><p>Copyright © 2004 Butterfield et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL.</p> The filled diamonds, as specified by the Unified Modelling language specification, indicate the object at which the diamonds end has the connected objects as essential components.