Question on run(sql[, stream])

[vitaliikalmykov]

Hello
We have the following command:
run(sql[, stream])
Runs the specified SQL command. Optionally, you can provide a stream for use with the COPY command.

I am assuming that I can use run to perform COPY command with some file-like stream object. Could you please advise how exactly COPY command should look like to consume data from second parameter - stream?
And additional question - do I understand correct that I can use run("copy...") for execute copy command without putting file to S3?