Question about get_metric and report_metric

Hi experts,
    In Innovus platform, I tried to use report_metric and get a huge list of metric items in it, however when I do get_metric only very few of them listed. Even I tried to use e.g. get_metric "check.place.outside_region_fence"  which is an item reported in report_metric output, it doesn't output anything, what have I done wrong and how can I get an item reported correctly using get_metric ?