/// <summary>
/// This method returns the list of genbankID with its corresponding molecule types.
/// Throws an exception of any error accessing the database occurs.
/// </summary>
public static XmlDocument listMoleculeTypes()
{
XmlDocument doc = new XmlDocument();
doc.AppendChild(dictionaryToXML(GDDL.listMoleculeTypes(), doc));
return(doc);
}