Draw an image in the current context figure.
    Parameters
    ----------
    image: image data
        Image data, depending on the passed format, can be one of:
            - an instance of an ipywidgets Image
            - a file name
            - a raw byte string
    format: {'widget', 'filename', ...}
        Type of the input argument.
        If not 'widget' or 'filename', must be a format supported by
        the ipywidgets Image.
    options: dict (default: {})
        Options for the scales to be created. If a scale labeled 'x' is
        required for that mark, options['x'] contains optional keyword
        arguments for the constructor of the corresponding scale type.
    axes_options: dict (default: {})
        Options for the axes to be created. If an axis labeled 'x' is required
        for that mark, axes_options['x'] contains optional keyword arguments
        for the constructor of the corresponding axis type.

def imshow(image, format, **kwargs):
    """Draw an image in the current context figure.
    Parameters
    ----------
    image: image data
        Image data, depending on the passed format, can be one of:
            - an instance of an ipywidgets Image
            - a file name
            - a raw byte string
    format: {'widget', 'filename', ...}
        Type of the input argument.
        If not 'widget' or 'filename', must be a format supported by
        the ipywidgets Image.
    options: dict (default: {})
        Options for the scales to be created. If a scale labeled 'x' is
        required for that mark, options['x'] contains optional keyword
        arguments for the constructor of the corresponding scale type.
    axes_options: dict (default: {})
        Options for the axes to be created. If an axis labeled 'x' is required
        for that mark, axes_options['x'] contains optional keyword arguments
        for the constructor of the corresponding axis type.
    """
    if format == 'widget':
        ipyimage = image
    elif format == 'filename':
        with open(image, 'rb') as f:
            data = f.read()
            ipyimage = ipyImage(value=data)
    else:
        ipyimage = ipyImage(value=image, format=format)
    kwargs['image'] = ipyimage

    kwargs.setdefault('x', [0., 1.])
    kwargs.setdefault('y', [0., 1.])

    return _draw_mark(Image, **kwargs)