code: def flesch_kincaid_grade_level(doc: Doc) -> float:
      """
      Readability test used widely in education, whose value estimates the U.S.
      grade level / number of years of education required to understand a text.
  
      Higher value => more difficult text.
  
      Args:
          doc
  
      References:
          https://en.wikipedia.org/wiki/Flesch%E2%80%93Kincaid_readability_tests#Flesch.E2.80.93Kincaid_grade_level
      """  # noqa: E501
      words = tuple(utils.get_words(doc))
      n_sents = basics.n_sents(doc)
      n_words = basics.n_words(words)
      n_syllables = basics.n_syllables(words, lang=doc.lang_)
      return (
          (11.8 * n_syllables / n_words)
          + (0.39 * n_words / n_sents)
          - 15.59
      )
  
file_path: textacy/src/textacy/text_stats/readability.py
imports: import logging
  import math
  import statistics
  from typing import Optional
  from spacy.tokens import Doc
  from ..None import errors
  from .None import basics, utils
label_desc: Use image node_id 4 for calling a global function with example usage: flesch_kincaid_grade_level(doc) and returns: unknown