code: def convert(self, verbose=True):
          
          input_transformer = self._input_class(self._filename)
          output_transformer = self._output_class()
  
          containers = input_transformer.ingest_containers()
  
          output_containers = []
  
          for container in containers:
              converted_container = self._convert_container(
                  container,
                  input_transformer,
                  output_transformer
              )
  
              validated = output_transformer.validate(converted_container)
  
              output_containers.append(validated)
  
          return output_transformer.emit_containers(output_containers, verbose)
docs: :rtype: tuple
          :returns: Output containers, messages