il_solvent_atomtype

il = mb.Compound()
solvent = mb.Compound()
for child in system.children:
    if child.name in ['bmim', 'tf2n']:
        il.add(mb.clone(child))
    elif child.name == 'acn':
        sollvent.add(mb.clone(child))
        
 opls = Forcefield(name='oplsaa')
 lopes = Forcefield('kpl.xml')
 
 ilPM = lopes.apply(il, residues=['bmim', 'tf2n'])
 solventPM = opls.apply(solvent, residues='acn')
 
 system = ilPM + solventPM