Remove unused 'warnings' imports.
Remove unused 're' imports.
Remove unused 'collections' imports.
Remove unused 'datetime' imports.
Remove unused 'operator' imports.
Remove unused 'os' imports.
Remove unused 'sys' imports.
Remove unused 'math' imports.
Remove unused 'mock' imports.
Remove unused 'OrderedDict' import.
Remove unused NumPy imports.
Remove unused 'biggus' imports.
Remove unused 'Image' import.
Remove unused Cartopy import.
Remove unused 'gribapi' imports.
Remove unused 'iris' imports.
Remove unused 'matplotlib' imports.
Remove unused 'netcdftime' import.
Remove unused 'iris.aux_factory' import.
Remove unused 'iris.coord*' imports.