How to use the micromagneticmodel.Demag function in micromagneticmodel

import micromagneticmodel as mm


class Demag(mm.Demag):
    """Demagnetisation energy term.

    This object models micromagnetic demagnetisation energy term. It
    does not take any mandatory arguments. However,
    `asymptotic_radius` and `name` can be passed.

    Parameters
    ----------
    asymptotic_radius : number.Real
      The asymptotic radius
    name: str (optional)
      Name of the energy term object. Defaults to `'demag'`

    Examples
    --------
    1. Initialising the demagnetisation energy term.