Create an instance from a dictionary.

def from_dict(cls, d):
        """
        Create an instance from a dictionary.
        """
        instance = super(SimulationGroup, cls).from_dict(d)
        #  instance.simulations is a list of dictionaries; convert each dictionary to a Simulation instance
        instance.simulations = [Simulation.from_dict(x) for x in instance.simulations]
        return instance