input: Write a python function to get the first 10 characters of a string.
  assert get_first_10_chars('Hello, world!') == 'Hello, wor'
  assert get_first_10_chars('Python programming') == 'Python pro'
  assert get_first_10_chars('1234567890abcdefgh') == '1234567890'
output: def get_first_10_chars(s):
      return s[:10]