input: Write a function to identify if a string contains an 'a' followed by zero or one 'b'.
  assert find_pattern("ac") == ('Found a match!')
  assert find_pattern("dc") == ('Not matched!')
  assert find_pattern("abbbba") == ('Found a match!')
output: def find_pattern(text):
      import re
      pattern = r'a(b?)'
      if re.search(pattern, text):
          return 'Found a match!'
      else:
          return 'Not matched!'