input: Write a function to generate a random number between two numbers provided as input. The function should take two parameters, which represent the minimum and maximum values, and return the generated random number. If either of the input values is negative, the function should return a message indicating that it only accepts positive numbers.
  assert random_number_generator(2, 5) in [2, 3, 4, 5]
  assert random_number_generator(10, 20) in range(10, 21)
  assert random_number_generator(-5, 5) == "Only positive numbers are accepted."
  assert random_number_generator(0, 0) == 0
output: import random
  
  def random_number_generator(min_val, max_val):
      if min_val < 0 or max_val < 0:
          return "Only positive numbers are accepted."
      return random.randint(min_val, max_val)