Syntax Sugar for `._select`

[0xMochan]

Is your feature request related to a problem? Please describe.
._select is pretty verbose, especially when forced to use it with keywords like "from"

subgraph.Query.snapshots._select("from")

Describe the solution you'd like
Use the subscript helpers for a cleaner syntax (and more intuitive)!

subgraph.Query.snapshots["from"]

Implementation checklist

• Add __setitem__ and __getitem__
• Add tests for those!