How to use the newick.tree.TreeVisitor function in newick

print item.organism, item.distance, item.domains, \
                item.statistics.get('Charge', '').strip()

class EnsemblComparaTranscript:
    """Hold comparative information retrieved from Ensembl on a transcript.
    """
    def __init__(self, organism, g_id, t_id, p_id):
        self.organism = organism
        self.g_id = g_id
        self.t_id = t_id
        self.p_id = p_id
        self.distance = None
        self.domains = []
        self.statistics = {}

class DistanceVisitor(newick.tree.TreeVisitor):
    def __init__(self):
        self.graph = networkx.Graph()
        
    def pre_visit_edge(self, src, b, l, dest):
        self.graph.add_edge(repr(src), repr(dest), l)

class EnsemblComparaRest:
    """Provide a REST-like API interface to Ensembl.
    """
    def __init__(self, cache_dir):
        self._base_url = "http://www.ensembl.org"
        self._cache_dir = cache_dir
        if not(os.path.exists(cache_dir)):
            os.makedirs(cache_dir)

    def protein_stats(self, organism, gene_id, tx_id):