def _fraction_elutions(fractions):
    """
    Given a list of fraction names, group them after removing 'FractionXX' from
    the end.  Return a dict of { elutionname: listofindices }.
    Example of fraction name: Orbitrap_HeLaCE_IEF_pH3_to_10_Fraction10
    """
    elution_names = {}
    for i,fname in enumerate(fractions):
        ename = fname[:fname.find('_Fraction')]
        elution_names.setdefault(ename,[]).append(i)
    return elution_names