KeyError: 'BlockType.DATASETS is not a valid block type'

using this prefix: prefix.tar.xz

edit the iris-pad-with-train toolchain, add a dataset:

Traceback (most recent call last):
  File "/home/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/toolchaineditor.py", line 767, in from_name
    return cls[name]
  File "/home/miniconda/envs/iris/lib/python3.7/enum.py", line 352, in __getitem__
    return cls._member_map_[name]
KeyError: <BlockType.DATASETS: 'datasets'>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/assetwidget.py", line 297, in __updateJsonWidget
    self.json_widget.setText(self.current_editor.dump_as_string())
  File "/home/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/editor.py", line 299, in dump_as_string
    self.dump_json(), sort_keys=True, indent=4, cls=utils.NumpyJSONEncoder
  File "/home/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/editor.py", line 292, in dump_json
    json_data.update(self._dump_json())
  File "/home/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/toolchaineditor.py", line 1939, in _dump_json
    return self.toolchain.dump()
  File "/home/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/toolchaineditor.py", line 1785, in dump
    if block_type == BlockType.from_name(block.type):
  File "/home/miniconda/envs/iris/lib/python3.7/site-packages/beat/editor/widgets/toolchaineditor.py", line 769, in from_name
    raise KeyError("{} is not a valid block type".format(name))
KeyError: 'BlockType.DATASETS is not a valid block type'