input: Write a function to calculate the distance between two points on a two-dimensional plane. The function should take two tuples, each representing a point (x, y), as input and return the distance as a float. If either point is invalid (i.e., not a tuple of two integers), the function should return None.
  assert calculate_distance((3, 4), (-9, -2)) == 13.0
  assert calculate_distance((0, 0), (0, 0)) == 0.0
  assert calculate_distance((1, 1), (1, 2)) == 1.0
  assert calculate_distance((5, -3), (5, 10)) == 13.0
  assert calculate_distance(("a", 4), (-9, -2)) == None
output: def calculate_distance(point1, point2):
      if not (isinstance(point1, tuple) and isinstance(point2, tuple) and len(point1) == 2 and len(point2) == 2 and isinstance(point1[0], int) and isinstance(point1[1], int) and isinstance(point2[0], int) and isinstance(point2[1], int)):
          return None
      return ((point1[0] - point2[0]) ** 2 + (point1[1] - point2[1]) ** 2) ** 0.5