input: Write a function that checks if a string contains an 'a' followed by either no 'b' or exactly one 'b'.
  assert text_match_zero_one("ac") == ('Found a match!')
  assert text_match_zero_one("dc") == ('Not matched!')
  assert text_match_zero_one("abbbba") == ('Found a match!')
output: def text_match_zero_one(text):
      import re
      pattern = r'a(b?)'
      if re.search(pattern, text):
          return 'Found a match!'
      else:
          return 'Not matched!'