code: def get_output_fields(self):
          
          # Re-engineer list from output format
          # XXX TODO: Would be better to use a FieldRecorder class to catch the full field names
          emit_fields = list(i.lower() for i in re.sub(r"[^_A-Z]+", ' ', self.format_item(None)).split())
  
          # Validate result
          result = []
          for name in emit_fields[:]:
              if name not in engine.FieldDefinition.FIELDS:
                  self.LOG.warn("Omitted unknown name '%s' from statistics and output format sorting" % name)
              else:
                  result.append(name)
  
          return result
docs: Get field names from output template.