def _FindAdobeIllustrator(f):
    """Does a file contain "Adobe_Illustrator"?

    Args:
      f: an open File
    Returns:
      bool: True if reading forward in f, we find "Adobe_Illustrator"
    """

    while True:
        s = f.readline()
        if not s or s.startswith(b"%%EndProlog"):
            break
        if s.find(b"Adobe_Illustrator") >= 0:
            return True
    return False