code: def _set_actual_container(self):
          
          # infer container format
          if self.container_format is None:
              self.log(u"Inferring actual container format...")
              path_lowercased = self.file_path.lower()
              self.log([u"Lowercased file path: '%s'", path_lowercased])
              self.container_format = ContainerFormat.UNPACKED
              for fmt in ContainerFormat.ALLOWED_FILE_VALUES:
                  if path_lowercased.endswith(fmt):
                      self.container_format = fmt
                      break
              self.log(u"Inferring actual container format... done")
              self.log([u"Inferred format: '%s'", self.container_format])
  
          # set the actual container
          self.log(u"Setting actual container...")
          class_map = {
              ContainerFormat.ZIP: (_ContainerZIP, None),
              ContainerFormat.EPUB: (_ContainerZIP, None),
              ContainerFormat.TAR: (_ContainerTAR, ""),
              ContainerFormat.TAR_GZ: (_ContainerTAR, ":gz"),
              ContainerFormat.TAR_BZ2: (_ContainerTAR, ":bz2"),
              ContainerFormat.UNPACKED: (_ContainerUnpacked, None)
          }
          actual_class, variant = class_map[self.container_format]
          self.actual_container = actual_class(
              file_path=self.file_path,
              variant=variant,
              rconf=self.rconf,
              logger=self.logger
          )
          self.log([u"Actual container format: '%s'", self.container_format])
          self.log(u"Setting actual container... done")
docs: Set the actual container, based on the specified container format.
  
          If the container format is not specified,
          infer it from the (lowercased) extension of the file path.
          If the format cannot be inferred, it is assumed to be
          of type :class:`~aeneas.container.ContainerFormat.UNPACKED`
          (unpacked directory).