l := gp.list(<list>)

Get a pointer to a container of all grid points in the model.

If a filter list is provided, the return value is a list of filtered grid points.

A filter list is a list of booleans of the same length as the number of grid points in the model, false values are filtered out.

Returns:l - a pointer to the list of all grid points, or a list of pointers to filtered grid points.