Figure out why coordinates are having an extra dimension added

[mattjbr123]

          Successfully run with parallelisation with this environment. 

Though I've now noticed that the pipeline has added a time dimension to the variables that we converted from data variables to coordinate variables in the preprocessing function (so the variables x_bnds, y_bnds and crs)

_Originally posted by @mattjbr123 in #9

[mattjbr123]

Spinning it off into it's own issue given it's a fairly minor problem at this stage

[mattjbr123]

The error will likely be in the pangeo functions that wrap around Beam, so that's probably the place to start...

[mattjbr123]

Following the advice here to find out which step of the pipeline the extra dimensions get added, as a starting point.

Annoyingly, a Beam print function can only be placed at the end of a Beam pipeline, (though my hunch is there is some more fancy syntax that allows for pipeline branching and works around this), so it's a case of one-by-one putting the print statement after each function and analysing the output until we see the extra dimensions added.

[mattjbr123]

Looks like it's to do with the ConsolidateDimensionCoordinates() function, which I guess isn't massively surprising... Will confirm and look into exactly what it's doing next.

[mattjbr123]

Something I may have forgotten - is this a bug that only occurs when running in parallel?
Need to check.

[mattjbr123]

Now I'm not so sure it's occuring with either. I'm currently unabled to reproduce the error, even with an identical setup AFAICT. So 🤞 this was a spurious bug or typo somewhere that has now resolved itself. I'm trying out a few scenarios to be sure.

[mattjbr123]

Seems to be miraculously resolved. I'll close this issue with a view to keeping an eye on things and reopening if it reoccurs.