Error "ReferenceError: serializeModule is not defined" with doc.serializeJSON()

[marcoexplora]

Hello,
We are using sboljs for elaborate a sbol XML and we see the following error when we use serializeJSON() function on complex SBOL with Module Nodes.

            return serializeModule(sbolDocument, module);
            ^

ReferenceError: serializeModule is not defined
    at /Users/marcoo/Documents/vue/sbojsdemo/node_modules/sboljs/lib/serialize/json/serializeModuleDefinition.js:50:13
    at Array.map (<anonymous>)
    at serializeModuleDefinition (/Users/marcoo/Documents/vue/sbojsdemo/node_modules/sboljs/lib/serialize/json/serializeModuleDefinition.js:49:48)
    at /Users/marcoo/Documents/vue/sbojsdemo/node_modules/sboljs/lib/serialize/json/serializeJSON.js:53:20
    at Array.map (<anonymous>)
    at SBOLDocument.serializeJSON (/Users/marcoo/Documents/vue/sbojsdemo/node_modules/sboljs/lib/serialize/json/serializeJSON.js:52:64)
    at SBOLDocument.serializeJSON (/Users/marcoo/Documents/vue/sbojsdemo/node_modules/sboljs/lib/SBOLDocument.js:913:58)
    at /Users/marcoo/Documents/vue/sbojsdemo/index.js:6:9
    at /Users/marcoo/Documents/vue/sbojsdemo/node_modules/sboljs/lib/SBOLDocument.js:865:17
    at /Users/marcoo/Documents/vue/sbojsdemo/node_modules/sboljs/lib/load/rdf/loadRDF.js:93:17```

Attached sources for reproduce this problem.
[sbolsource.zip](https://github.com/SynBioDex/sboljs/files/5809423/sbolsource.zip)

Thanks in advance for any suggestion 



Marco