Improvements 
Improvements 

Check data file exits.
Use path to assembly in `AddReference`
move pandas symbol slicing
AnshulYADAV007/Lean,JKarathiya/Lean,AlexCatarino/Lean,kaffeebrauer/Lean,kaffeebrauer/Lean,AlexCatarino/Lean,kaffeebrauer/Lean,StefanoRaggi/Lean,jameschch/Lean,StefanoRaggi/Lean,StefanoRaggi/Lean,JKarathiya/Lean,jameschch/Lean,Jay-Jay-D/LeanSTP,kaffeebrauer/Lean,QuantConnect/Lean,AnshulYADAV007/Lean,AnshulYADAV007/Lean,QuantConnect/Lean,AnshulYADAV007/Lean,Jay-Jay-D/LeanSTP,AnshulYADAV007/Lean,StefanoRaggi/Lean,JKarathiya/Lean,Jay-Jay-D/LeanSTP,kaffeebrauer/Lean,jameschch/Lean,jameschch/Lean,Jay-Jay-D/LeanSTP,StefanoRaggi/Lean,AlexCatarino/Lean,jameschch/Lean,QuantConnect/Lean,AlexCatarino/Lean,JKarathiya/Lean,QuantConnect/Lean,Jay-Jay-D/LeanSTP