input: Write a python function to calculate the coefficient of determination (R2 score) for two given lists x and y.
  assert calculateR2([1, 2, 3], [1, 2, 3]) == 1.0
  assert calculateR2([1, 2, 3], [2, 2, 2]) == 0.0
  assert calculateR2([1, 2, 3, 4], [1.1, 2.1, 3.1, 4.1]) > 0.99
output: def calculateR2(x, y):
      mean_y = sum(y) / len(y)
      ss_total = sum((yi - mean_y) ** 2 for yi in y)
      ss_residual = sum((yi - xi) ** 2 for xi, yi in zip(x, y))
      r2 = 1 - (ss_residual / ss_total)
      return r2