I have a suggestion for the units.ConversionInterface class.
It seems to me that for each method of the ConversionInterface there should be
another parameter passed in, the Axis instance that is requesting the conversion/info.
Doing so would allow for any custom conversion code to make checks on the Axis,
whether it is X/Y, or even make checks on the Axes the Axis is attached to. Additionally
this would allow for converters to apply any necessary changes before they are
really used (such as DateConverter making sure that the axis bounds are >=
If it is okay, I would like to apply the necessary changes.