code: def vra(self,*args,**kwargs):
          
          from .OrbitTop import _check_roSet, _check_voSet
          _check_roSet(self,kwargs,'vra')
          _check_voSet(self,kwargs,'vra')
          dist= self._orb.dist(*args,**kwargs)
          if _APY_UNITS and isinstance(dist,units.Quantity):
              out= units.Quantity(dist.to(units.kpc).value*_K*
                                  self._orb.pmra(*args,**kwargs)\
                                      .to(units.mas/units.yr).value,
                                  unit=units.km/units.s)
          else:
              out= dist*_K*self._orb.pmra(*args,**kwargs)
          if len(out) == 1: return out[0]
          else: return out
docs: NAME:
  
             vra
  
          PURPOSE:
  
             return velocity in right ascension (km/s)
  
          INPUT:
  
             t - (optional) time at which to get vra (can be Quantity)
  
             obs=[X,Y,Z,vx,vy,vz] - (optional) position and velocity of observer 
                           in the Galactocentric frame
                           (in kpc and km/s) (default=[8.0,0.,0.,0.,220.,0.]; entries can be Quantity)
                           OR Orbit object that corresponds to the orbit
                           of the observer
                           Y is ignored and always assumed to be zero
  
             ro= (Object-wide default) physical scale for distances to use to convert (can be Quantity)
  
             vo= (Object-wide default) physical scale for velocities to use to convert (can be Quantity)
  
          OUTPUT:
  
             v_ra(t) in km/s
  
          HISTORY:
  
             2011-03-27 - Written - Bovy (NYU)