def forward(ctx, input_, weight, bias):
        """
        **Overview**:
            Forward implementation of linear layer.
        """
        # Save parameters for backward.
        ctx.save_for_backward(input_, weight)
        # Forward calculation: $$output = input \cdot weight^T + bias$$
        output = input_.mm(weight.t())
        output += bias
        return output

        **Overview**:
            Forward implementation of linear layer.
        
chapter3_obs/gradient.py