code: def inc_from_lat(lat):
      
      rad = old_div(np.pi, 180.)
      inc = old_div(np.arctan(2 * np.tan(lat * rad)), rad)
      return inc
docs: Calculate inclination predicted from latitude using the dipole equation
  
      Parameter
      ----------
      lat : latitude in degrees
  
      Returns
      -------
      inc : inclination calculated using the dipole equation