def METHOD_NAME(a_str, b_str):
  """
    Returns a short portion of the text that shows the first difference
    @ In, a_str, string, the first text element
    @ In, b_str, string, the second text element
    @ Out, short_text, string, resulting shortened diff
  """
  a_str = repr(a_str)
  b_str = repr(b_str)
  display_len = 20
  half_display = display_len//2
  if len(a_str)+len(b_str) < display_len:
    return a_str+" "+b_str
  first_diff = -1
  i = 0
  while i < len(a_str) and i < len(b_str):
    if a_str[i] == b_str[i]:
      i += 1
    else:
      first_diff = i
      break
  if first_diff >= 0:
    #diff in content
    start = max(0, first_diff - half_display)
  else:
    #diff in length
    first_diff = min(len(a_str), len(b_str))
    start = max(0, first_diff - half_display)
  if start > 0:
    prefix = "..."
  else:
    prefix = ""
  return prefix+a_str[start:first_diff+half_display]+" "+prefix+\
    b_str[start:first_diff+half_display]