input: Write a function to convert a list of strings to uppercase.
  assert convert_to_uppercase(['this', 'is', 'a', 'list', 'of', 'strings']) == ['THIS', 'IS', 'A', 'LIST', 'OF', 'STRINGS']
  assert convert_to_uppercase(['hello', 'world']) == ['HELLO', 'WORLD']
  assert convert_to_uppercase(['python', 'code']) == ['PYTHON', 'CODE']
output: def convert_to_uppercase(lst):
      return [s.upper() for s in lst]