Check, if ds_to_write = dataset["headers]] increases the memory usage #584

We need to check, if the following increases the memory usage:

ds_to_write = dataset["headers]]
ds_to_write["headers"].data[not_null] = traces.header
ds_to_write["headers"].data[~not_null] = 0

due to creating a copy or the original large data array ds_to_write
We hope that ds_to_write is instead references to the data array in dataset