input: from typing import List
  
  
  def perform_linear_regression(X: List[float], Y: List[float]) -> str:
      """ Perform linear regression using the provided dataset and predict the value of y for x = 7.
      >>> perform_linear_regression([1, 2, 3, 4, 5], [3, 5, 7, 9, 13])
      '[15.0]'
      """
output:     n = len(X)
      sum_X = sum(X)
      sum_Y = sum(Y)
      sum_XY = sum(x * y for x, y in zip(X, Y))
      sum_X_squared = sum(x ** 2 for x in X)
      
      m = (n * sum_XY - sum_X * sum_Y) / (n * sum_X_squared - sum_X ** 2)
      b = (sum_Y - m * sum_X) / n
      
      y_pred = m * 7 + b
      
      return f'[{y_pred}]'