docs: def _create_structure(self):
          """Create necessary structure to hold a dataset."""
  
          # Ensure that the specified path does not exist and create it.
          if os.path.exists(self._abspath):
              raise(StorageBrokerOSError(
                  "Path already exists: {}".format(self._abspath)
              ))
  
          # Make sure the parent directory exists.
          parent, _ = os.path.split(self._abspath)
          if not os.path.isdir(parent):
              raise(StorageBrokerOSError(
                  "No such directory: {}".format(parent)))
  
          os.mkdir(self._abspath)
  
          # Create more essential subdirectories.
          for abspath in self._essential_subdirectories:
              if not os.path.isdir(abspath):
                  os.mkdir(abspath)