input: Write a function to calculate the center of a cube given its vertices.
  assert calculate_center([(0, 0, 0), (1, 0, 0), (0, 1, 0), (1, 1, 0), (0, 0, 1), (1, 0, 1), (0, 1, 1), (1, 1, 1)]) == (0.5, 0.5, 0.5)
  assert calculate_center([(1, 1, 1), (2, 1, 1), (1, 2, 1), (2, 2, 1), (1, 1, 2), (2, 1, 2), (1, 2, 2), (2, 2, 2)]) == (1.5, 1.5, 1.5)
  assert calculate_center([(0, 0, 0), (0, 0, 4), (0, 4, 0), (0, 4, 4), (4, 0, 0), (4, 0, 4), (4, 4, 0), (4, 4, 4)]) == (2, 2, 2)
output: def calculate_center(vertices):
      x_coords = [v[0] for v in vertices]
      y_coords = [v[1] for v in vertices]
      z_coords = [v[2] for v in vertices]
      
      center_x = sum(x_coords) / len(x_coords)
      center_y = sum(y_coords) / len(y_coords)
      center_z = sum(z_coords) / len(z_coords)
      
      return (center_x, center_y, center_z)