def __init__(self, rules):
        if isinstance(rules, dict):
            rules = rules.items()
        found = set()
        self.abstract = []
        for key, expr in rules:
            if key not in _plural_tags:
                raise ValueError('unknown tag %r' % key)
            elif key in found:
                raise ValueError('tag %r defined twice' % key)
            found.add(key)
            self.abstract.append((key, _Parser(expr).ast))
Determine outer indices of an Add object.
dataset/ETHPy150Open mbr/Babel-CLDR/babel/plural.py/PluralRule.__init__--crossover with--dataset/ETHPy150Open sympy/sympy/sympy/tensor/index_methods.py/_get_indices_Add