added test to hit KeyError when variable with same name in storage.
added "alias" key option to dataset dictionary.
before chaning iterators to work with multivariate calculations.
before converting to storing multivariate calculations as variables.
before modifying iterators.
morning.
minor.
added keyed test to multiple datasets.
added check for unique spatial dimension.
before modifying geometry identifier to not look for unique.
added fix for speed with geometries. iteration is still slow.
minor.
morning commit.
before simplifying EqualSpatialDimensionMapper.
before removing code from subset.
before add level mapper.
working keyed iterator for multiple datasets.
fixed bug with value keyed iterator.
all tests working.
before incorporating alias logic into query reduction.