Fix JSON-LD load errors

[lambdamusic]

The simple periodical.json test JSON-LD fails loading:

{
  "@context": "http://schema.org/",
  "@graph": [
    {
        "@id": "#issue",
        "@type": "PublicationIssue",
        "issueNumber": "5",
        "datePublished": "2012",
        "isPartOf": {
            "@id": "#periodical",
            "@type": [
                "PublicationVolume",
                "Periodical"
            ],
            "name": "Cataloging & Classification Quarterly",
            "issn": [
                "1544-4554",
                "0163-9374"
            ],
            "volumeNumber": "50",
            "publisher": "Taylor & Francis Group"
        }
    },
    {
        "@type": "ScholarlyArticle",
        "isPartOf": "#issue",
        "description": "The library catalog as a catalog of works was an infectious idea, which together with research led to reconceptualization in the form of the FRBR conceptual model. Two categories of lacunae emerge--the expression entity, and gaps in the model such as aggregates and dynamic documents. Evidence needed to extend the FRBR model is available in contemporary research on instantiation. The challenge for the bibliographic community is to begin to think of FRBR as a form of knowledge organization system, adding a final dimension to classification. The articles in the present special issue offer a compendium of the promise of the FRBR model.",
        "sameAs": "https://doi.org/10.1080/01639374.2012.682254",
        "about": [
            "Works",
            "Catalog"
        ],
        "pageEnd": "368",
        "pageStart": "360",
        "name": "Be Careful What You Wish For: FRBR, Some Lacunae, A Review",
        "author": "Smiraglia, Richard P."
    }
  ]
}

This is due to an RDFLIB issue, documented here:

RDFLib/rdflib#1423

[lambdamusic]

UPDATE: the rdflib fix should be coming in the near future. So, till then, no point in adding any extra logic to ontospy to deal with this bug.

[lambdamusic]

Now fixed

[lambdamusic]

https://github.com/lambdamusic/Ontospy/releases/tag/2.0.0-alpha