def METHOD_NAME(self, fileno):
    try:
        filename = self._filemap[fileno]
    except KeyError:
        print "Could not identify fileId", fileno
        return 1
    if filename is None:
        return 1
    absname = os.path.normcase(os.path.join(self.cwd, filename))
    try:
        fp = open(absname)
    except IOError:
        return
    st = parser.suite(fp.read())
    fp.close()
    # Scan the tree looking for def and lambda nodes, filling in
    # self._funcmap with all the available information.
    funcdef = symbol.funcdef
    lambdef = symbol.lambdef
    stack = [st.totuple(1)]
    while stack:
        tree = stack.pop()
        try:
            sym = tree[0]
        except (IndexError, TypeError):
            continue
        if sym == funcdef:
            self._funcmap[(fileno, tree[2][2])] = filename, tree[2][1]
        elif sym == lambdef:
            self._funcmap[(fileno, tree[1][2])] = filename, "<lambda>"
        stack.extend(list(tree[1:]))