optimize and add new service of get report and download report.

model/GST.py

@@ -10,7 +10,7 @@ class GST:
         invoices_rows = invoice_crud.GetAllData(storedproc="GetAllInvoicesBasic")
 
         if not invoice_crud.isSuccess:
-            return []  
+            return []  # Could also log invoice_crud.resultMessage
 
         invoices = [
             dict(
@@ -25,16 +25,16 @@ class GST:
         gst_rows = gst_crud.GetAllData(storedproc="GetAllGSTReleasesBasic")
 
         if not gst_crud.isSuccess:
-            return [] 
+            return []  # Could also log gst_crud.resultMessage
 
         gst_invoice_nos = {
-            g[2] 
+            g[2]  # Invoice_No is at index 2
             for g in gst_rows
             if g[2]
         }
 
         gst_basic_amounts = {
-            float(g[3]) 
+            float(g[3])  # Basic_Amount at index 3
             for g in gst_rows
             if g[3] is not None
         }