code: def flesch_reading_ease(
      doc: Doc, *, lang: Optional[str] = None
  ) -> float:
      """
      Readability test used as a general-purpose standard in several languages, based on
      a weighted combination of avg. sentence length and avg. word length. Values usually
      fall in the range [0, 100], but may be arbitrarily negative in extreme cases.
  
      Higher value => easier text.
  
      Args:
          doc
          lang
  
      Note:
          Coefficients in this formula are language-dependent;
          if ``lang`` is null, the value of ``Doc.lang_`` is used.
  
      References:
          English: https://en.wikipedia.org/wiki/Flesch%E2%80%93Kincaid_readability_tests#Flesch_reading_ease
          German: https://de.wikipedia.org/wiki/Lesbarkeitsindex#Flesch-Reading-Ease
          Spanish: Fernández-Huerta formulation
          French: ?
          Italian: https://it.wikipedia.org/wiki/Formula_di_Flesch
          Dutch: ?
          Portuguese: https://pt.wikipedia.org/wiki/Legibilidade_de_Flesch
          Turkish: Atesman formulation
          Russian: https://ru.wikipedia.org/wiki/%D0%98%D0%BD%D0%B4%D0%B5%D0%BA%D1%81_%D1%83%D0%B4%D0%BE%D0%B1%D0%BE%D1%87%D0%B8%D1%82%D0%B0%D0%B5%D0%BC%D0%BE%D1%81%D1%82%D0%B8
      """  # noqa: E501
      if lang is None:
          lang = doc.lang_
      try:
          coefs = _FRE_COEFS[lang]
      except KeyError:
          raise ValueError(
              errors.value_invalid_msg(
                  "lang", lang, list(_FRE_COEFS.keys())
              )
          )
  
      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=lang)
      return (
          coefs["base"]
          - (coefs["asl"] * n_words / n_sents)
          - (coefs["awl"] * n_syllables / n_words)
      )
  
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 5 for calling a global function with example usage: flesch_reading_ease(doc) and returns: unknown