LegendEntry does not contain delete element when serialised
*Created originally on Bitbucket by [CharlieC](https://bitbucket.org/%7B32d660d5-f934-4ce5-a7b0-52750378fae1%7D/)* The following class should include a delete tag when serialised ``` #!python legendEntry = LegendEntry(0, delete=True) ``` ``` #!xml <legendEntry> <idx val="0" /> <delete val="1" /> </legendEntry> ``` But the delete tag is missing.
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