code: def is_text_extractor_available(extension: str) -> bool:
      
      if extension is not None:
          extension = extension.lower()
      info = ext_map.get(extension)
      if info is None:
          return False
      availability = info[AVAILABILITY]
      if type(availability) == bool:
          return availability
      elif callable(availability):
          return availability()
      else:
          raise ValueError(
              "Bad information object for extension: {}".format(extension))
docs: Is a text extractor available for the specified extension?