Function write 

pub fn write(
    model: &Model,
    roots: &[Shape],
    options: WriteOptions,
) -> OgeomResult<String>

Write a model, and the shapes it is a document about.

roots are recorded so a reader gets back the same handles the writer had. A model with no roots is legal (it is a document of loose geometry), but a reader then has nothing to start a traversal from.

Errors

OgeomError::Construction if the model holds something this does not know how to write, which is refused rather than dropped, or if a root does not resolve in the model.