Functions that are declared but not defined will cause the micropython build to fail, since it would assume, from file header, that these functions are available and will try to call them (linker error)
when we want to add set data by `lv_chart_set_next` to a chart in `LV_CHART_MODE_CIRCULAR` mode we don't need to invalidate the whole chart object so these functions are added to just invalidate the added data area.
