Definitions of Event in SBML Level 2 Versions 1 and 2 included the additional attribute called "timeUnits", but it was removed in SBML Level 2 Version 3. LibSBML supports this attribute for compatibility with previous versions of SBML Level 2, but its use is discouraged since models in Level 2 Versions 3 and 4 cannot contain it. If a Version 3 or 4 model sets the attribute, the consistency-checking method SBMLDocument::checkConsistency() will report an error.
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