Refactors GetSymbolsFromPyObject method
Refactors GetSymbolsFromPyObject method

GetSymbolsFromPyObject now returns IEnumerable<Symbol> and throws if its argument is not Symbol or Symbol[] object and if the Symbol has not been added to the Securities object.

StefanoRaggi/Lean,Jay-Jay-D/LeanSTP,kaffeebrauer/Lean,kaffeebrauer/Lean,AnshulYADAV007/Lean,redmeros/Lean,jameschch/Lean,QuantConnect/Lean,AnshulYADAV007/Lean,AlexCatarino/Lean,AnshulYADAV007/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,JKarathiya/Lean,Jay-Jay-D/LeanSTP,JKarathiya/Lean,jameschch/Lean,kaffeebrauer/Lean,AnshulYADAV007/Lean,jameschch/Lean,redmeros/Lean,QuantConnect/Lean,redmeros/Lean,JKarathiya/Lean,Jay-Jay-D/LeanSTP,StefanoRaggi/Lean,AnshulYADAV007/Lean,kaffeebrauer/Lean,QuantConnect/Lean,AlexCatarino/Lean,jameschch/Lean,Jay-Jay-D/LeanSTP,redmeros/Lean,Jay-Jay-D/LeanSTP,QuantConnect/Lean,kaffeebrauer/Lean,StefanoRaggi/Lean,AlexCatarino/Lean,StefanoRaggi/Lean,JKarathiya/Lean,jameschch/Lean