add the precision display : update eval_map.py

[0Freeebaby]

Add the precision display, fix in eval_map.py
So that other learners can learn to use the framework better.

Problem: lack of classification precision of display detectors

[CLAassistant]

All committers have signed the CLA.

[yangxue0827]

Please delete all comments # add precision @0Freeebaby

[0Freeebaby]

I am very sorry for seeing the message so late, I have deleted all comments。