def chunksizes(
        self,
    ) -> Mapping[_Dim, _Shape]:
        """
        Mapping from dimension names to block lengths for this NamedArray's data.

        If this NamedArray does not contain chunked arrays, the mapping will be empty.

        Cannot be modified directly, but can be modified by calling .chunk().

        Differs from NamedArray.chunks because it returns a mapping of dimensions to chunk shapes
        instead of a tuple of chunk shapes.

        See Also
        --------
        NamedArray.chunk
        NamedArray.chunks
        xarray.unify_chunks
        """
        data = self._data
        if isinstance(data, _chunkedarray):
            return dict(zip(self.dims, data.chunks, strict=True))
        else:
            return {}

        Mapping from dimension names to block lengths for this NamedArray's data.

        If this NamedArray does not contain chunked arrays, the mapping will be empty.

        Cannot be modified directly, but can be modified by calling .chunk().

        Differs from NamedArray.chunks because it returns a mapping of dimensions to chunk shapes
        instead of a tuple of chunk shapes.

        See Also
        --------
        NamedArray.chunk
        NamedArray.chunks
        xarray.unify_chunks
        
xarray/namedarray/core.py