input: Write a python function to count the number of vowels and consonants in a given string.
  assert count_vowels_and_consonants('This is a sample string') == (5, 14)
  assert count_vowels_and_consonants('Hello World') == (3, 7)
  assert count_vowels_and_consonants('Python Programming') == (4, 13)
output: def count_vowels_and_consonants(s):
      vowels = "aeiouAEIOU"
      num_vowels = sum(1 for char in s if char in vowels)
      num_consonants = sum(1 for char in s if char.isalpha() and char not in vowels)
      return num_vowels, num_consonants