input: Write a python function to find the length of the longest contiguous sequence of 1's in a binary string.
  assert countMaxOnes("101101111") == 3
  assert countMaxOnes("111111") == 6
  assert countMaxOnes("0000") == 0
  assert countMaxOnes("10001") == 1
  assert countMaxOnes("101010101") == 1
output: def countMaxOnes(binary_string):
      max_count = 0
      current_count = 0
      
      for char in binary_string:
          if char == '1':
              current_count += 1
              max_count = max(max_count, current_count)
          else:
              current_count = 0
      
      return max_count