This is a filter for a small pond / fountain pump to allow it to be used directly in a pond and filter out weed, tadpoles and general grot which would clog up the impeller.
This is not for the really small pump type which have an inbuilt filter; this is the next size up with a tubular 12mm o.d. inlet and no filter - See the spec label photo.

Print this with no support and with the inlet side down as per the STL. The roof is a good test of your printer's bridging capability; a head fan helps here. Don't worry about stringing between the holes as it will help the filter action.
The inlet is intentionally slightly undersize. Use a sharp edge to scrape the inside to give a good twisting fit, but carefully as the filter is a bit brittle (at least it is with PLA).