Values of a Dask Dataframe
I have to transform the dask dataframe to json format and 

You may be interested in the .to_json method of Dask dataframes

and to do that I should get the values.

This may not be true
Is there a way to get values of a dask dataframe without using compute function as pandas? 

Pandas: df.values
Dask using compute function: ddf.compute().values

Dask using compute function is slow and I have to transform the dask dataframe to json format and to do that I should get the values.