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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 _make_plus_helper(obj, fields):
 """ add a + prefix to any fields in obj that aren't in fields """

    new_obj = {}

    for key, value in obj.items():
        if key in fields or key.startswith('_'):
            # if there's a subschema apply it to a list or subdict
            if fields.get(key):
                if isinstance(value, list):
                    value = [_make_plus_helper(item, fields[key])
                             for item in value]
            # assign the value (modified potentially) to the new_obj
            new_obj[key] = value
        else:
            # values not in the fields dict get a +
            new_obj['+%s' % key] = value

    return new_obj