feat(python)!: allow from_arrow to take a generator of RecordBatches, change error type to TypeError

[alexander-beedie]

Slightly extends pl.from_arrow constructor to allow a generator of RecordBatch as input (which the underlying pa.Table.from_batches method accepts).

---

As well as being convenient, might offer some modest memory advantages if receiving multiple batches (started looking into allowing read_database to take connection objects, and snowflake has a fetch_arrow_batches method, for example) vs requiring up-front single-batch materialisation. Need to check the pyarrow source to see how it's handled there to confirm that though.

[stinodego]

Can't we just accept an Iterable and let pa.Table.from_batches do the work? I'm taking a closer look here.

[stinodego]

I added a commit with what I think is a simpler implementation. What do you think? Feel free to reset / do things differently, of course, but I thought this would be the simplest way to show my thinking.

[alexander-beedie]

Can't we just accept an Iterable and let pa.Table.from_batches do the work?

Not if we want to generate the same error when a generator containing an incorrect type is passed-in; if we don't mind being a bit inconsistent then yes.

Having said that, technically we're actually raising the wrong class of error here; should be a TypeError (as pa.Table.from_batches would raise), not a ValueError, but I was going to fix that as a breaking update afterwards 😅

How about I fix it up (making it a TypeError) and simplify as Iterable at the same time, and we push it out with 0.19? Two birds, one stone... The error text in this edge-case would be slightly different when given an incorrectly-typed generator, but at least the errors (raised by us or raised by pyarrow) will both be of the same class.

Update:
Ahh, I see you already changed the exception type in your commit - shall we tag as breaking? Otherwise the update/simplification looks A-Ok to me 👌

[stinodego]

All right then, this can be merged! I'll let you do the honors :)

Related: I think we can improve error types in many areas, I'll make a round sometime to do some updates.