get modelVersion() {
        return this.version;
    }
Load a graph model given a synchronous IO handler with a 'load' method.

@param modelSource The `io.IOHandlerSync` that loads the model, or the
    `io.ModelArtifacts` that encode the model, or a tuple of
    `[io.ModelJSON, ArrayBuffer]` of which the first element encodes the
     model and the second contains the weights.

@doc {heading: 'Models', subheading: 'Loading'}