class_docstr: 构建 **NG20** 数据集的 **Graph** 。
  
  :param graph_type: 
  :param widow_size:
  :param threshold:
class_docstr_tok: ["\u6784\u5efa","*","*","NG20","*","*","\u6570\u636e\u96c6\u7684","*","*","Graph","*","*","\u3002",":","param","graph_type",":",":","param","widow_size",":",":","param","threshold",":"]
code: def __init__(self, graph_type="pmi", widow_size=10, threshold=0.0):
      super().__init__(
          graph_type=graph_type,
          widow_size=widow_size,
          threshold=threshold,
      )
  
imports: from collections import defaultdict
  import itertools
  import math
  import numpy
  from ..data_bundle import DataBundle
  from ..loader.classification import MRLoader, OhsumedLoader, R52Loader, R8Loader, NG20Loader
  from fastNLP.core.utils import f_rich_progress
label_desc: Use image node_id 1 to create a new NG20PmiGraphPipe object from inherited base classes: GraphBuilderBase with example: obj = NG20PmiGraphPipe(graph_type, widow_size, threshold)