code: def handleClash1(userName, existing=[], prefix="", suffix=""):
      """
      existing should be a case-insensitive list
      of all existing file names.
  
      >>> prefix = ("0" * 5) + "."
      >>> suffix = "." + ("0" * 10)
      >>> existing = ["a" * 5]
  
      >>> e = list(existing)
      >>> handleClash1(userName="A" * 5, existing=e,
      ...		prefix=prefix, suffix=suffix) == (
      ... 	'00000.AAAAA000000000000001.0000000000')
      True
  
      >>> e = list(existing)
      >>> e.append(prefix + "aaaaa" + "1".zfill(15) + suffix)
      >>> handleClash1(userName="A" * 5, existing=e,
      ...		prefix=prefix, suffix=suffix) == (
      ... 	'00000.AAAAA000000000000002.0000000000')
      True
  
      >>> e = list(existing)
      >>> e.append(prefix + "AAAAA" + "2".zfill(15) + suffix)
      >>> handleClash1(userName="A" * 5, existing=e,
      ...		prefix=prefix, suffix=suffix) == (
      ... 	'00000.AAAAA000000000000001.0000000000')
      True
      """
      # if the prefix length + user name length + suffix length + 15 is at
      # or past the maximum length, silce 15 characters off of the user name
      prefixLength = len(prefix)
      suffixLength = len(suffix)
      if (
          prefixLength + len(userName) + suffixLength + 15
          > maxFileNameLength
      ):
          l = prefixLength + len(userName) + suffixLength + 15
          sliceLength = maxFileNameLength - l
          userName = userName[:sliceLength]
      finalName = None
      # try to add numbers to create a unique name
      counter = 1
      while finalName is None:
          name = userName + str(counter).zfill(15)
          fullName = prefix + name + suffix
          if fullName.lower() not in existing:
              finalName = fullName
              break
          else:
              counter += 1
          if counter >= 999999999999999:
              break
      # if there is a clash, go to the next fallback
      if finalName is None:
          finalName = handleClash2(existing, prefix, suffix)
      # finished
      return finalName
  
label_desc: Use image node_id 2 for calling a global function with example usage: handleClash1(userName, existing, prefix, suffix) and returns: finalName