code: def requires_ocr(filename):
      """
      ```
      Uses pdffonts program to determine if the PDF requires OCR, i.e., it
      doesn't contain any fonts.
      :param filename: of PDF file
      :return: True if requires OCR, False if not
      ```
      """
      output = Popen(
          ["pdffonts", filename], stdout=PIPE, stderr=DEVNULL
      ).communicate()[0]
      return len(output.split("\n")) < 4
  
imports: from subprocess import DEVNULL, PIPE, Popen
  from ..imports import *
label_desc: Use image node_id 6 for calling a global function with example usage: requires_ocr(filename) and returns: unknown