Update internals.py

Author: vmalaviya-splunk

splunklib/searchcommands/internals.py

@@ -594,7 +594,8 @@ def _write_record(self, record):
         fieldnames = self._fieldnames
 
         if fieldnames is None:
-            self._fieldnames = fieldnames = set(list(record.keys())) | self.custom_fields
+            self._fieldnames = fieldnames = list(record.keys())
+            self._fieldnames.extend(self.custom_fields)
             value_list = imap(lambda fn: (str(fn), str('__mv_') + str(fn)), fieldnames)
             self._writerow(list(chain.from_iterable(value_list)))