text: import numpy as np
  from prml.nn.function import Function
  
  
  class Sqrt(Function):
  
      def _forward(self, x):
          self.output = np.sqrt(x)
          return self.output
  
      def _backward(self, delta, x):
          return 0.5 * delta / self.output
  
  
  def sqrt(x):
      return Sqrt().forward(x)
  