code: def _import_mapping(mapping, original=None):
      
      #log = get_logger()
      #log.debug("Importing canning map")
      for key, value in list(mapping.items()):
          if isinstance(key, string_types):
              try:
                  cls = import_item(key)
              except Exception:
                  if original and key not in original:
                      # only message on user-added classes
                      # log.error("canning class not importable: %r", key, exc_info=True)
                      print("ERROR: canning class not importable: %r", key, exc_info=True)
                  mapping.pop(key)
              else:
                  mapping[cls] = mapping.pop(key)
docs: Import any string-keys in a type mapping.