class BaseView:
    '''
    BaseView class, from which all views inherit. Implements the 
        following functions:
    '''

    def __init__(self):
        pass

    def view(self, im):
        '''
        Apply transform to an image.

        im (`torch.tensor`):
            For stage 1: Tensor of shape (3, H, W) representing a noisy image
            OR
            For stage 2: Tensor of shape (6, H, W) representing a noisy image
            concatenated with an upsampled conditioning image from stage 1
        '''
        raise NotImplementedError()

    def inverse_view(self, noise):
        '''
        Apply inverse transform to noise estimates.
            Because DeepFloyd estimates the variance in addition to
            the noise, this function must apply the inverse to the
            variance as well.

        im (`torch.tensor`):
            Tensor of shape (6, H, W) representing the noise estimate
            (first three channel dims) and variacne estimates (last
            three channel dims)
        '''
        raise NotImplementedError()

    def make_frame(self, im, t):
        '''
        Make a frame, transitioning linearly from the identity view (t=0) 
            to this view (t=1)

        im (`PIL.Image`) :
            A PIL Image of the illusion

        t (float) :
            A float in [0,1] indicating time in the animation. Should start
            at the identity view at t=0, and continuously transition to the
            view at t=1.
        '''
        raise NotImplementedError()