Get all `SampleRelation`s in the relation graph of the sample.

        :param depth: max depth of the returned graph. None retrieves the complete graph.
        :return: An iterator over the relations

def get_relation_graph(self, depth=None):
        """
        Get all `SampleRelation`s in the relation graph of the sample.

        :param depth: max depth of the returned graph. None retrieves the complete graph.
        :return: An iterator over the relations
        """
        url = '{}relation_graph/'.format(self.url)
        if depth is not None:
            params = {'depth': depth}
        else:
            params = {}

        from .sample_relation import SampleRelation
        return SampleRelation._get_iter_from_url(url, params=params, append_base_url=False)