code: def _ensure_correct_weights(self, *weights):
      for w in weights:
          if w < 0.0:
              raise ValueError("Negative weights are not allowed.")
  
imports: from __future__ import absolute_import
  from __future__ import division, print_function, unicode_literals
  from collections import defaultdict
  from ..nlp.stemmers import null_stemmer
  from ._summarizer import AbstractSummarizer
  from .edmundson_cue import EdmundsonCueMethod
  from .edmundson_key import EdmundsonKeyMethod
  from .edmundson_title import EdmundsonTitleMethod
  from .edmundson_location import EdmundsonLocationMethod
label_desc: Use image node_id 2 for calling the EdmundsonSummarizer obj's underlying member method code with example usage: obj._ensure_correct_weights() without return types