code: def _prop_descriptions(self):
      return """\
          opacity
              Sets the marker opacity of unselected points, applied
              only when a selection exists.
          """
  
imports: from plotly.basedatatypes import BaseTraceHierarchyType
  import copy
label_desc: Use image node_id 3 for calling the Marker obj's underlying member method code with example usage: obj._prop_descriptions() and returns: str