'Args:
tensor_name (str): the name of the tensor.
prefix (str): the filename prefix for saved images. Defaults to the Op name.
map_func: map the value of the tensor to an image or list of
images of shape [h, w] or [h, w, c]. If None, will use identity.
scale (float): a multiplier on pixel values, applied after map_func.'

def __init__(self, tensor_name, prefix=None, map_func=None, scale=255):

    (op_name, self.tensor_name) = get_op_tensor_name(tensor_name)
    self.func = map_func
    if (prefix is None):
        self.prefix = op_name
    else:
        self.prefix = prefix
    self.log_dir = logger.LOG_DIR
    self.scale = scale
