2.1.0

New features

• Users can now use the MultiContainerInterface class to generate custom API classes that contain collections of
  containers of a specified type. @bendichter @rly (#399)
  • See the user guide
    https://hdmf.readthedocs.io/en/stable/tutorials/multicontainerinterface.html for more information.

Internal improvements

• Add ability to pass callable functions to run when adding or removing items from a LabelledDict.
  An error is now raised when using unsupported functionality in LabelledDict. @rly (#405)
• Raise a warning when building a container that is missing a required dataset. @rly (#413)