The attribute "font-weight" is used to specify whether the text is to be "normal" or "bold". If omitted, the text may be rendered in either way. In the SBML Level 3 Version 1 Render specification, the following are the allowable values for "font-weight":
"bold", darker and/or thicker than normal print.
"normal", the typical print weight; lighter and/or thinner than "bold".
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