code: def append_cluster_attribute(self, index_canvas, index_cluster, data, marker = None, markersize = None):
          
          
          cluster_descr = self.__canvas_clusters[index_canvas][index_cluster]
          attribute_marker = marker
          if attribute_marker is None:
              attribute_marker = cluster_descr.marker
          
          attribure_markersize = markersize
          if attribure_markersize is None:
              attribure_markersize = cluster_descr.markersize
          
          attribute_color = cluster_descr.color
          
          added_attribute_cluster_descriptor = canvas_cluster_descr(data, None, attribute_marker, attribure_markersize, attribute_color)
          self.__canvas_clusters[index_canvas][index_cluster].attributes.append(added_attribute_cluster_descriptor)
docs: !
          @brief Append cluster attribure for cluster on specific canvas.
          @details Attribute it is data that is visualized for specific cluster using its color, marker and markersize if last two is not specified.
          
          @param[in] index_canvas (uint): Index canvas where cluster is located.
          @param[in] index_cluster (uint): Index cluster whose attribute should be added.
          @param[in] data (list): List of points (data) that represents attribute.
          @param[in] marker (string): Marker that is used for displaying objects from cluster on the canvas.
          @param[in] markersize (uint): Size of marker.