input: Write a python function to check for missing colons in loop statements.
  assert check_missing_colons('for num in numbers') == True
  assert check_missing_colons('for num in numbers:') == False
  assert check_missing_colons('while True') == True
  assert check_missing_colons('while True:') == False
output: def check_missing_colons(statement):
      statement = statement.strip()
      if (statement.startswith('for ') or statement.startswith('while ')) and not statement.endswith(':'):
          return True
      return False