def METHOD_NAME(self):
    filename = os.path.join(self._path, "trees", "tree_0_0_0.dat")
    f = open(filename)
    while True:
        l = f.readline()
        if l.startswith("#tree"):
            break
    read_type = np.dtype([
              ('id_this', np.int64),
              ('id_desc', np.int64),
              ('phantom', np.int8),
              ('Mvir', np.float32)])
    results = np.loadtxt(f, usecols=(1,3,8,10), dtype=read_type)
    self.links = results