datachain: generalize data access functions into collect(), and collect_flatten

[skshetry]

Closes #67.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.85%. Comparing base (7f7ed1a) to head (ffa5c72).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #121      +/-   ##
==========================================
+ Coverage   85.71%   86.85%   +1.13%     
==========================================
  Files          93       88       -5     
  Lines        9493     9364     -129     
  Branches     1897     1876      -21     
==========================================
- Hits         8137     8133       -4     
+ Misses       1024      899     -125     
  Partials      332      332              

Flag	Coverage Δ
datachain	86.78% <100.00%> (+1.13%)	⬆️

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View logs

[ilongin]

LGTM, now it's much clearer how to fetch data as those redundant methods were confusing.

[dberenbaum]

@skshetry We should coordinate this with #111. Are you ready to merge this, or should I go ahead with #111?

[skshetry]

Feel free to merge. I will handle conflicts (if any) and merge in the morning.

[rlamy]

I wish there was a way to force the output to be a tuple, working with a variable cols is going to be awkward otherwise as the corner cases of len(cols) in [0,1] need to be handled.

[skshetry]

I agree. One idea that I have is we can make the first argument to be (arg: tuple[str] | str, *args: str).

But that complicates signature.

[dmpetrov]

LGTM!