code: def drop_neutral_categories_from_corpus(self):
  		'''
  		Returns
  		-------
  		PriorFactory
  		'''
  		neutral_categories = self._get_neutral_categories()
  		self.term_doc_mat = self.term_doc_mat.remove_categories(neutral_categories)
  		self._reindex_priors()
  		return self drop_neutral_categories_from_corpus(self):
  		'''
  		Returns
  		-------
  		PriorFactory
  		'''
  		neutral_categories = self._get_neutral_categories()
  		self.term_doc_mat = self.term_doc_mat.remove_categories(neutral_categories)
  		self._reindex_priors()
  		return self
docs: Returns
  		-------
  		PriorFactory