const bson_t *
const mongoc_apm_command_failed_t *event);
Returns the server’s reply to a command that failed. The reply contains details about why the command failed. If no server reply was received, such as in the event of a network error, then the reply is a valid empty BSON document. The data is only valid in the scope of the callback that receives this event; copy it if it will be accessed after the callback returns.
event: A mongoc_apm_command_failed_t.
bson_t that should not be modified or freed.