All species properties as a dict

def properties(self):
        """All species properties as a dict"""
        properties = {'id': self._id,
                      'boundary': self._boundary}
        if 'name' in self._root.attrib:
            properties['name'] = self._root.get('name')
        if 'compartment' in self._root.attrib:
            properties['compartment'] = self._root.get('compartment')

        charge = self.charge
        if charge is not None:
            properties['charge'] = charge

        formula = self.formula
        if formula is not None:
            properties['formula'] = formula

        return properties