code: def prepData4Call(self,*args,**kwargs):
          
          #First calculate the actionAngle coordinates if they're not given 
          #as such
          freqsAngles= self._parse_call_args(*args,**kwargs)
          dOmega= freqsAngles[:3,:]\
              -numpy.tile(self._progenitor_Omega.T,(freqsAngles.shape[1],1)).T
          dangle= freqsAngles[3:,:]\
              -numpy.tile(self._progenitor_angle.T,(freqsAngles.shape[1],1)).T
          #Assuming single wrap, resolve large angle differences (wraps should be marginalized over)
          dangle[(dangle < -4.)]+= 2.*numpy.pi
          dangle[(dangle > 4.)]-= 2.*numpy.pi
          return (dOmega,dangle)
docs: NAME:
             prepData4Call
          PURPOSE:
             prepare stream data for the __call__ method
          INPUT:
             __call__ inputs
          OUTPUT:
             (dOmega,dangle); wrt the progenitor; each [3,nobj]
          HISTORY:
             2013-12-04 - Written - Bovy (IAS)