input: Write a python function to retrieve the prime numbers from a dictionary where prime numbers are keys.
  assert get_prime_numbers() == [2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
  prime_dict = {3: True, 5: True, 7: True}
  assert get_prime_numbers() == [3, 5, 7]
output: def get_prime_numbers(prime_dict={2: True, 3: True, 5: True, 7: True, 11: True, 13: True, 17: True, 19: True, 23: True, 29: True}):
      return sorted([key for key in prime_dict if prime_dict[key]])