def _dummy(name, token, expr, **kwargs):
    """
    Return a dummy. This will return the same dummy if the same token+name is
    requested more than once, and it is not already in expr.
    This is for being cache-friendly.
    """
    d = _dummy_(name, token, **kwargs)
    if d in expr.free_symbols:
        return Dummy(name, **kwargs)
    return d
dataset/ETHPy150Open sympy/sympy/sympy/integrals/meijerint.py/_dummy/original