code: def define_user_analysis_extent(self, extent, crs):
          
          extent = QgsGeometry.fromRect(extent)
          self.extent.set_user_extent(extent, crs)
          self.validate_impact_function()
docs: Slot called when user has defined a custom analysis extent.
  
          .. versionadded: 2.2.0
  
          :param extent: Extent of the user's preferred analysis area.
          :type extent: QgsRectangle
  
          :param crs: Coordinate reference system for user defined analysis
              extent.
          :type crs: QgsCoordinateReferenceSystem