def __init__(self, grammar, beam_size=0, trace=0):
        if not isinstance(grammar, PCFG):
            raise ValueError("The grammar must be probabilistic PCFG")
        self._grammar = grammar
        self.beam_size = beam_size
        self._trace = trace
Create a new ``BottomUpProbabilisticChartParser``, that uses
dataset/ETHPy150Open nltk/nltk/nltk/parse/pchart.py/BottomUpProbabilisticChartParser.__init__