code: def vhel_to_vgsr(coordinate, vhel, vsun):
      
  
      if vsun is None:
          vsun = coord.Galactocentric.galcen_v_sun.to_cartesian().xyz
  
      return vhel + _get_vproj(coordinate, vsun)
docs: Convert a velocity from a heliocentric radial velocity to
      the Galactic standard of rest (GSR).
  
      Parameters
      ----------
      coordinate : :class:`~astropy.coordinates.SkyCoord`
          An Astropy SkyCoord object or anything object that can be passed
          to the SkyCoord initializer.
      vhel : :class:`~astropy.units.Quantity`
          Barycentric line-of-sight velocity.
      vsun : :class:`~astropy.units.Quantity`
          Full-space velocity of the sun in a Galactocentric frame. By default,
          uses the value assumed by Astropy in
          `~astropy.coordinates.Galactocentric`.
  
      Returns
      -------
      vgsr : :class:`~astropy.units.Quantity`
          Radial velocity in a galactocentric rest frame.