It was a mistake from my side regarding the data.Please find below the the corrected sample data.Also the name of the sample data file is being passed to load_sketch() as the $sketch_file string.

Sample data

sgw sketch sgwpts1 format EMS,SGW1,%date%,%time%,%sgw-vpnname%,%sgw-vp
+nid%,%sgw-servname%,%sgw-servid%
sgw sketch sgwptsh format EMS,SGWh,%date%,%time%,%sgw-vpnname%,%sgw-vp
+nid%,%sgw-servname%,%sgw-servid%
sgw sketch sgwptsi format EMS,SGWi,%date%,%time%,%sgw-vpnname%,%sgw-vp
+nid%,%sgw-servname%,%sgw-servid%
sgw sketch sgwptsH format EMS,SGWH,%date%,%time%,%sgw-vpnname%,%sgw-vp
+nid%,%sgw-servname%,%sgw-servid%
sgw sketch sgwptsI format EMS,SGWI,%date%,%time%,%sgw-vpnname%,%sgw-vp
+nid%,%sgw-servname%,%sgw-servid%
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