input: Write a python function to return a list of all prime numbers less than or equal to a given number.
  assert get_primes(20) == [2, 3, 5, 7, 11, 13, 17, 19]
  assert get_primes(10) == [2, 3, 5, 7]
  assert get_primes(2) == [2]
  assert get_primes(1) == []
  assert get_primes(0) == []
output: def get_primes(n):
      def is_prime(k):
          if k <= 1:
              return False
          for i in range(2, int(k**0.5) + 1):
              if k % i == 0:
                  return False
          return True
  
      return [x for x in range(2, n + 1) if is_prime(x)]