input: Write a python function to count the number of uppercase and lowercase letters in a given string.
  assert count_uppercase_lowercase("This Is A Test String") == (5, 12)
  assert count_uppercase_lowercase("Hello World!") == (2, 8)
  assert count_uppercase_lowercase("PYTHON programming") == (6, 11)
output: def count_uppercase_lowercase(s):
      uppercase_count = sum(1 for char in s if char.isupper())
      lowercase_count = sum(1 for char in s if char.islower())
      return (uppercase_count, lowercase_count)