Pyhomogenize

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* add time bounds if length of time axis is 1
* convert np.datetime64 object to CFTimeIndex

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* published on zenodo

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* testing for python version 3.8, 3.9 and 3.10

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* read and write data with length of time axis is 1
* add time bounds with length of time axis is 1
* drop coordinates from non CF variables

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* get CF_variables

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* calculate time_bnds and add them to dataset