Iterator over :class:`SpeciesEntries <.SpeciesEntry>`

        This will not yield boundary condition species if those are ignored.

def species(self):
        """Iterator over :class:`SpeciesEntries <.SpeciesEntry>`

        This will not yield boundary condition species if those are ignored.
        """
        return (c for c in itervalues(self._model_species)
                if not self._ignore_boundary or not c.boundary)