code: def moduli_to_velocities(rho, K_s, G):
      
      return np.sqrt(K_s / rho), np.sqrt(G / rho)
docs: convert moduli to velocities
      mainly to support Burnman operations
  
      :param rho: density in kg/m^3
      :param v_phi: adiabatic bulk modulus in Pa
      :param v_s: shear modulus in Pa
      :return: bulk sound speed and shear velocity