Get the number of atoms in the calculated structure.

        Returns: Property, where number of atoms is a scalar.

def get_number_of_atoms(self):
        """Get the number of atoms in the calculated structure.

        Returns: Property, where number of atoms is a scalar.
        """
        strc = self.get_output_structure()
        if not strc:
            return None
        return Property(scalars=[Scalar(value=len(strc))], units="/unit cell")