input: Write a function to add two numbers together and print the result. The function should take two parameters and return the sum of the two numbers. If any of the inputs are not numbers, the function should return None.
  
  
  def add(a, b):
      if not isinstance(a, (int, float)) or not isinstance(b, (int, float)):
          return None
      return a + b
  
  assert add(5, 7) == 12
  assert add(3.5, 4.2) == 7.7
  assert add("5", 7) == None
  assert add(5, "7") == None
  assert add(10, -3) == 7
  
output: def add(a, b):
      if not isinstance(a, (int, float)) or not isinstance(b, (int, float)):
          return None
      return a + b