def list_branches(filename, treename=None):
return _librootnumpy.list_branches(filename, treename)<EOL>
Get a list of the branch names of a tree in a ROOT file.

    Parameters
    ----------
    filename : str
        Path to ROOT file.
    treename : str, optional (default=None)
        Name of tree in the ROOT file.
        (optional if the ROOT file has only one tree).

    Returns
    -------
    branches : list
        List of branch names