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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _parse_field_arguments(arg, faces, edges, coords):
    '''See mesh_register.'''
    if not hasattr(arg, '__iter__'):
        raise RuntimeError('field argument must be a list-like collection of instructions')
    pot = [_parse_field_argument(instruct, faces, edges, coords) for instruct in arg]
    # make a new Potential sum unless the length is 1
    if len(pot) <= 1:
        return pot[0]
    else:
        sp = java_link().jvm.nben.mesh.registration.Fields.newSum()
        for field in pot: sp.addField(field)
        return sp