langchain/tools/shell/tool.py/ShellInput/_validate_commands
class ShellInput:    def _validate_commands(cls, values: dict) -> dict:
        """Validate commands."""
        # TODO: Add real validators
        commands = values.get("commands")
        if not isinstance(commands, list):
            values["commands"] = [commands]
        # Warn that the bash tool is not safe
        warnings.warn(
            "The shell tool has no safeguards by default. Use at your own risk."
        )
        return values