Writing files larger than memory

[moloney]

During some of the recent DICOM -> Nifti conversations we discussed this need. It was mentioned that it wasn't really possible with the current API, but it was probably feasible to create an API where a memmap plus some other info (scaling?) is passed in to achieve this goal. @matthew-brett @ZviBaratz @effigies

[ZviBaratz]

Are we talking about a single DICOM series that is larger than memory? I'm not really familiar with any clean, existing way to handle larger-than-memory data structures without introducing dask as a dependency as well (of course there are other options, but I think dask would be best suited).