input: Write a python function to check if a string contains two consecutive same characters.
  assert check_for_two_same_chars("hello")==True
  assert check_for_two_same_chars("world")==False
  assert check_for_two_same_chars("bookkeeper")==True
output: def check_for_two_same_chars(s):
      for i in range(len(s) - 1):
          if s[i] == s[i + 1]:
              return True
      return False