'Define the cost function and its gradient as lambda functions.'

def __init__(self, sigma=1.0):

    self.sigma = sigma
    self._sigma2 = self.be.square(sigma)
    self.func = (lambda y, t: self.be.sum(self.smoothL1((y - t)), axis=0))
    self.funcgrad = (lambda y, t: self.smoothL1grad((y - t)))
