(self, ixreader, fieldname, model=Bo1Model)
:param reader: A :class:whoosh.reading.IndexReader object.
        :param fieldname: The name of the field in which to search.
        :param model: (classify.ExpansionModel) The model to use for expanding
            the query terms. If you omit this parameter, the expander uses
            :class:`Bo1Model` by default.
:param reader: A :class:whoosh.reading.IndexReader object.
        :param fieldname: The name of the field in which to search.
        :param model: (classify.ExpansionModel) The model to use for expanding
            the query terms. If you omit this parameter, the expander uses
            :class:`Bo1Model` by default.
: param reader : A : class : whoosh . reading . IndexReader object . : param fieldname : The name of the field in which to search . : param model : ( classify . ExpansionModel ) The model to use for expanding the query terms . If you omit this parameter the expander uses : class : Bo1Model by default .
def __init__(self, ixreader, fieldname, model=Bo1Model):
        """
        :param reader: A :class:whoosh.reading.IndexReader object.
        :param fieldname: The name of the field in which to search.
        :param model: (classify.ExpansionModel) The model to use for expanding
            the query terms. If you omit this parameter, the expander uses
            :class:`Bo1Model` by default.
        """

        self.ixreader = ixreader
        self.fieldname = fieldname
        doccount =  self.ixreader.doc_count_all()
        fieldlen = self.ixreader.field_length(fieldname)

        if type(model) is type:
            model = model(doccount, fieldlen)
        self.model = model

        # Maps words to their weight in the top N documents.
        self.topN_weight = defaultdict(float)

        # Total weight of all terms in the top N documents.
        self.top_total = 0
def __init__ ( self , ixreader , fieldname , model = Bo1Model ) : self . ixreader = ixreader self . fieldname = fieldname doccount = self . ixreader . doc_count_all ( ) fieldlen = self . ixreader . field_length ( fieldname ) if type ( model ) is type : model = model ( doccount , fieldlen ) self . model = model # Maps words to their weight in the top N documents. self . topN_weight = defaultdict ( float ) # Total weight of all terms in the top N documents. self . top_total = 0