XML Loader: need to read incoming accessionCodes from user and check to see if already loaded to VegBank
VegBranch accession codes for a user are matched to existing VegBank
accessionCodes through userDatasetItem table- when an xml file is split into
multiple files for the sake of file size. Our loader needs to look into this
table for a user to see if the accessionCode a user is giving us has already
been loaded. If so, match to the element with matching AccCode instead of adding
new element. This is already properly done within one XML file's load.