def cmd(command: str, timeout_seconds: Optional[float] = None) -> str:
"""Run a command and capture its output to stdout and stderr into a
string buffer. Return that string as this function's output.
def cmd(command: str, timeout_seconds: Optional[float] = None) -> str:
"""Run a command and capture its output to stdout and stderr into a
string buffer. Return that string as this function's output.