input: Write a python function to calculate the slope and intercept of a linear regression line given two lists of x and y values.
  assert calculate_slope_intercept([1, 2, 3, 4], [2, 4, 6, 8]) == (2.0, 0.0)
  assert calculate_slope_intercept([1, 2, 3], [1, 2, 3]) == (1.0, 0.0)
  assert calculate_slope_intercept([1, 3, 5], [2, 4, 6]) == (1.0, 1.0)
output: def calculate_slope_intercept(x, y):
      n = len(x)
      sum_x = sum(x)
      sum_y = sum(y)
      sum_xy = sum(x_i * y_i for x_i, y_i in zip(x, y))
      sum_x2 = sum(x_i ** 2 for x_i in x)
  
      slope = (n * sum_xy - sum_x * sum_y) / (n * sum_x2 - sum_x ** 2)
      intercept = (sum_y - slope * sum_x) / n
  
      return slope, intercept