Cover the \n in flex.

[Shylock-Hg]

What type of PR is this?

• bug
• feature
• enhancement

What does this PR do?

Which issue(s)/PR(s) this PR relates to?

Special notes for your reviewer, ex. impact of this fix, etc:

Additional context:

Checklist：

• Documentation affected （Please add the label if documentation needs to be modified.)
• Incompatible （If it is incompatible, please describe it and add corresponding label.）
• Need to cherry-pick （If need to cherry-pick to some branches, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes：

Please confirm whether to reflect in release notes and how to describe:

                                                            `

[codecov-commenter]

Codecov Report

Merging #3461 (5d919dc) into master (9a0fbb6) will decrease coverage by 0.19%.
The diff coverage is 86.31%.

@@            Coverage Diff             @@
##           master    #3461      +/-   ##
==========================================
- Coverage   85.40%   85.21%   -0.20%     
==========================================
  Files        1289     1304      +15     
  Lines      119798   121223    +1425     
==========================================
+ Hits       102317   103301     +984     
- Misses      17481    17922     +441     

Impacted Files	Coverage Δ
src/clients/meta/MetaClient.h	95.65% <ø> (ø)
src/common/graph/Response.h	45.66% <ø> (ø)
src/common/time/TimezoneInfo.cpp	50.00% <ø> (+4.54%)	⬆️
src/graph/executor/admin/AddHostsExecutor.cpp	0.00% <0.00%> (ø)
src/graph/executor/admin/AddHostsExecutor.h	0.00% <0.00%> (ø)
src/graph/executor/admin/DropHostsExecutor.cpp	0.00% <0.00%> (ø)
src/graph/executor/admin/DropHostsExecutor.h	0.00% <0.00%> (ø)
src/graph/executor/admin/ShowHostsExecutor.h	100.00% <ø> (ø)
src/graph/planner/plan/Admin.cpp	52.45% <0.00%> (-3.69%)	⬇️
src/graph/planner/plan/PlanNode.h	81.25% <ø> (ø)
... and 141 more

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