input: Write a function to generate a random number between two given numbers. If the input numbers are equal, return the input number. If the input numbers are invalid (e.g., not valid numbers), return None.
  assert random_number_generator(2, 5) in [2, 3, 4, 5]
  assert random_number_generator(5, 5) == 5
  assert random_number_generator("", 5) == None
  assert random_number_generator(2, "a") == None
output: import random
  
  def random_number_generator(a, b):
      try:
          a = float(a)
          b = float(b)
          if a == b:
              return a
          return random.randint(min(a, b), max(a, b))
      except ValueError:
          return None