Improve 'partial' documentation

[adamchainz]

Is your feature request related to a problem? Please describe.

I don't understand the statement "Element attributes are partially matched by default." Does it mean attrs={"id": "foo"} will match attrs={"id": "foob"} ?

Describe the solution you'd like

Better description with examples of what would/would not be matched with partial=True vs False.

Describe alternatives you've considered

n/a

Additional information

n/a