Format the following sentence by adding quotation marks wherever necessary.
I always wondered why she called me sweetheart
"I always wondered why she called me sweetheart."
Complete the following task based on the instruction and optional input provided.### Instruction:
Format the following sentence by adding quotation marks wherever necessary.

### Input:
I always wondered why she called me sweetheart

### Output:
"I always wondered why she called me sweetheart."