@classmethod
def poisson(cls, mu, x):
    """
        Visualization for a Poisson distribution
        Args:
            mu, x (float): parameters to a Poisson distribution
        Returns:
            image (IPython.display.Image): The image that can be displayed inline in a Jupyter notebook
        """
    if not isinstance(x, int):
        raise ValueError(
            'For a Poisson distribution, x should always be an integer.')
    if x < 0:
        raise ValueError(
            'For a Poisson distribution, x should be greater than or equal to zero.'
            )
    if mu <= 0:
        raise ValueError(
            'For a Poisson distribution, mu should be greater than zero.')
    return cls._call_post(dist='poisson', mu=mu, x=x)
