def history(self):
        """
        Ordered Dictionary of lists with the evolution of
        the data as function of the relaxation step.
        """
        history = OrderedDict()
        for cycle in self:
            d = cycle.last_iteration
            for k, v in d.items():
                if k in history:
                    history[k].append(v)
                else:
                    history[k] = [v]

        # Convert to numpy arrays.
        for k, v in history.items():
            history[k] = np.array(v)

        return history
def history ( self ) : history = OrderedDict ( ) for cycle in self : d = cycle . last_iteration for k , v in d . items ( ) : if k in history : history [ k ] . append ( v ) else : history [ k ] = [ v ] for k , v in history . items ( ) : history [ k ] = np . array ( v ) return history
Ordered Dictionary of lists with the evolution of
        the data as function of the relaxation step.