text: import math as math
  import numpy as np
  
  # MAPE Mean Absolute Percentage Error
  def mape(y_true, y_pred):
      total = 0
      for index in range(len(y_true)):
          total = total + abs((y_true[index] - y_pred[index])/(y_true[index]))
      return total/len(y_true)
  
  # RMSE Root Mean Squared Error
  def rmse(y_true, y_pred):
      total = 0
      for index in range(len(y_true)):
          total = total + pow((y_true[index] - y_pred[index]),2)
      total = total / len(y_true)
      return math.sqrt(total)
  
  # SSR Sum Squared Residuals
  def ssr(y_true, y_pred):
      return np.sum(np.square(y_true - y_pred))
  