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If there are any errors, none of the data will be imported.
What If Report
Click the purple 
What If report button to generate a CSV report of what would be changed if the file were imported.
When the report is ready to be downloaded, the button will turn green 
click the button to download.
If there are any errors, these will be shown in the same way as when importing and the report will not be generated.
Viewing errors
If there are any errors when validating the file during importing or generating the what if report, the import will show the Error status as above.
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