input: Write a function to calculate the area of a triangular pyramid.
  assert area(5, 4, 6, 2, 3, 5) == 31.0
  assert area(3, 4, 5, 6, 7, 8) == 46.5
  assert area(1, 1, 1, 1, 1, 1) == 1.5
output: def area(a, b, c, h1, h2, h3):
      base_area = 0.5 * a * h1
      side_area1 = 0.5 * b * h2
      side_area2 = 0.5 * c * h3
      total_area = base_area + side_area1 + side_area2
      return total_area