Generate an example sentence using the idiom " let the cat out of the bag".
Sarah accidentally let the cat out of the bag about the surprise party we were planning for our friend's birthday.
Complete the following task based on the instruction and optional input provided.### Instruction:
Generate an example sentence using the idiom " let the cat out of the bag".

### Output:
Sarah accidentally let the cat out of the bag about the surprise party we were planning for our friend's birthday.