Fix Bug where _wrap handles Pandas DFs incorrectly

[geenen124]

Closes #97

[EntilZha]

Thanks for the PR!

I took a look at the failed tests, and they look unrelated to the PR (version of lint checker upgraded and code hasn't been changed to adapt yet).

Things look good to me with the exception of a cleaner way of skipping the test if pandas isn't installed which I'll mention in a sec. Once that is changed then I'll merge, and fix those random lint errors.

[codecov-io]

Codecov Report

Merging #122 into master will decrease coverage by 1.42%. The diff coverage is 80%.

@@            Coverage Diff             @@
##           master     #122      +/-   ##
==========================================
- Coverage    99.9%   98.47%   -1.43%     
==========================================
  Files          12       12              
  Lines        2149     2169      +20     
==========================================
- Hits         2147     2136      -11     
- Misses          2       33      +31

Impacted Files	Coverage Δ
functional/pipeline.py	99.25% <71.42%> (-0.75%)	:arrow_down:
functional/test/test_functional.py	99.73% <84.61%> (-0.27%)	:arrow_down:
functional/io.py	90.9% <0%> (-9.1%)	:arrow_down:
functional/transformations.py	96.44% <0%> (-3.56%)	:arrow_down:
functional/test/test_streams.py	98.16% <0%> (-1.84%)	:arrow_down:
functional/util.py	98.41% <0%> (-1.59%)	:arrow_down:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 9459ee3...60061ae. Read the comment docs.

[geenen124]

I've used a similar decorator to the one you suggested :+1:

[EntilZha]

Thanks for the fix! Great work, LGTM to merge