Function init_logging_at 

pub fn init_logging_at(level: LevelFilter)

Install the stderr logger at an explicit verbosity. Idempotent in the sense that the first caller wins the global log backend registration; every call (re-)applies the requested max level, so an embedding can call init_logging() early and later raise the level via init_logging_at (e.g. the Python set_log_level shim) without losing the override. This is how a caller opts back into the verbose Info/debug/trace solver trace that the Warn default suppresses for performance (#1688).