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supportsOutputMIMEList allows you to constrain the output formats available to selection to the ones you specify. Multiple outputMime elements can be nested inside this element.
The sametop-level, non-nested outputMIME element selects sets CSV as the preferred default output format.
The list of currently-supported report output MIME types can be found in the default reportMimeTypes option list configuration.
The above config looks redundant: why specify a preferred output format when there is only one output format? Indeed, the report can be run without specifying the default output format. However, the non-nested/top-level outputMIME value is used to populate the Default output format in the Tools > Reports screen, so it is best to provide this information.
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TODO: Test whether it is necessary to specify the selected outputMIME if only one format is supported.
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