input: Write a python function to filter out strings that contain a specific letter and are in uppercase.
  assert sort_upper(['HELLO', 'WORLD', 'PYTHON', 'CODE'], 'O') == ['WORLD', 'CODE']
  assert sort_upper(['JAVA', 'javascript', 'KOTLIN', 'swift'], 'T') == ['KOTLIN']
  assert sort_upper(['APPLE', 'banana', 'CHERRY', 'date'], 'E') == ['APPLE', 'CHERRY']
output: def sort_upper(strings, letter):
      return [s for s in strings if letter in s and s.isupper()]