input: Write a function to implement a Caesar cipher.
  assert caesar_cipher('HELLO', 3) == 'KHOOR'
  assert caesar_cipher('WORLD', 5) == 'BTWQI'
  assert caesar_cipher('PYTHON', 10) == 'ZIDRYX'
output: def caesar_cipher(text, shift):
      result = []
      for char in text:
          if char.isalpha():
              shift_amount = shift % 26
              new_char = chr((ord(char) - 65 + shift_amount) % 26 + 65)
              result.append(new_char)
          else:
              result.append(char)
      return ''.join(result)