'We prepend an F to folders.'

def to_dict(self, view='collection', value_mapper=None):

    rval = super(Library, self).to_dict(view=view, value_mapper=value_mapper)
    if ('root_folder_id' in rval):
        rval['root_folder_id'] = ('F' + str(rval['root_folder_id']))
    return rval
