fix use_as_lib example

[taojy123]

Sorry for my mistake, #1542

[codecov]

Codecov Report

Merging #1543 into master will decrease coverage by 0.19%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1543      +/-   ##
==========================================
- Coverage   82.89%   82.69%   -0.20%     
==========================================
  Files          28       28              
  Lines        2566     2566              
  Branches      391      391              
==========================================
- Hits         2127     2122       -5     
- Misses        343      348       +5     
  Partials       96       96              

Impacted Files	Coverage Δ
locust/runners.py	84.62% <0.00%> (-0.57%)	⬇️
locust/web.py	91.37% <0.00%> (-0.44%)	⬇️
locust/stats.py	90.68% <0.00%> (-0.21%)	⬇️

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[cyberw]

Thanks!