input: Write a python function to format a string such that if more than 66% of the characters are spaces, it converts the string to uppercase.
  assert format_string("Hello World")== "HELLO WORLD"
  assert format_string("Python Programming")== "Python Programming"
  assert format_string("This is a test string")== "THIS IS A TEST STRING"
output: def format_string(s):
      space_count = s.count(' ')
      if space_count / len(s) > 0.66:
          return s.upper()
      return s