def GridInterpolator(grid_obj):
    """ 
      Interpolates the energy grid based on scipy's RegularGridInterpolator with default settings.

      :type grid_obj: instance of the grid3D class
      :param grid_obj: contains all the information regarding the energy grid used in isotherm prediction
    
      :raises: ValueError
    
      :rtype: An interpolator function of the type RegularGridInterpolator from scipy.interpolate
      """
    from scipy.interpolate import RegularGridInterpolator
    pot_interp = RegularGridInterpolator((grid_obj.X, grid_obj.Y, grid_obj.
        Z), grid_obj.pot_repeat)
    return pot_interp
