Generate a population of :math:`\lambda` individuals.

        Notes
        -----
        Individuals are of type *ind_init* from the current strategy.

        Parameters
        ----------
        ind_init:
            A function object that is able to initialize an
            individual from a list.

def _generate(self, func):
        """Generate a population of :math:`\lambda` individuals.

        Notes
        -----
        Individuals are of type *ind_init* from the current strategy.

        Parameters
        ----------
        ind_init:
            A function object that is able to initialize an
            individual from a list.
        """
        arz = numpy.random.standard_normal((self.lambda_, self.dim))
        arz = self.centroid + self.sigma * numpy.dot(arz, self.BD.T)
        self.population = list(map(func, arz))
        return