``attr`` forms ``closed_or_open`` curve
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Usages:
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 - **Given** *It forms an open curve*

   :doc:`/features/GEM111_No-duplicated-points-within-a-polyloop-or-polyline`:18

 - **Given** *It forms a closed curve*

   :doc:`/features/GEM111_No-duplicated-points-within-a-polyloop-or-polyline`:25

 - **Given** *It forms a closed curve*

   :doc:`/features/GEM111_No-duplicated-points-within-a-polyloop-or-polyline`:32