code: def dipole_moment(r_array, charge_array):
      '''Return the dipole moment of a neutral system.
      '''
      return np.sum(r_array * charge_array[:, np.newaxis], axis=0f dipole_moment(r_array, charge_array):
      '''Return the dipole moment of a neutral system.
      '''
      return np.sum(r_array * charge_array[:, np.newaxis], axis=0)
docs: Return the dipole moment of a neutral system.