'Initialize the fprop optree for batchnorm.'

def get_forward_optree(self):

    xvar = self.be.var(self.x, axis=1)
    xmean = self.be.mean(self.x, axis=1)
    xhat = ((self.x - xmean) / self.be.sqrt((xvar + self.eps)))
    return ((xhat * self.gamma) + self.beta)
