Update internals.py

Author: vmalaviya-splunk

splunklib/searchcommands/internals.py

@@ -594,8 +594,8 @@ def _write_record(self, record):
         fieldnames = self._fieldnames
 
         if fieldnames is None:
-            self.custom_fields |= set(record.keys())
-            self._fieldnames = fieldnames = list(self.custom_fields)
+            self._fieldnames = fieldnames = list(record.keys())
+            self._fieldnames.extend([i for i in self.custom_fields if i not in self._fieldnames])
             value_list = imap(lambda fn: (str(fn), str('__mv_') + str(fn)), fieldnames)
             self._writerow(list(chain.from_iterable(value_list)))