I have tested a lua function:

```
function handleFigure(el)
   ... --- some code to get the figure and caption object 
   if caption.content[1] then
        figure.caption = caption.content[1]
        print(TableToStr(figure))
   end
   ---figure.title = 'fig:'
   return pandoc.Para{ figure }
end
```

The printed info as below shows the caption is set correctly.
```
{['attr']={['identifier']='',['classes']={},['attributes']={}},['caption']={['content']={{['text']='xxx'},{},{['text']='yyy'}}},['src']='img/logo.png',['title']=''}
```
But the resulting latex is (What I expected is a floating figure since it has a caption)
```
\includegraphics{img/logo.png}
```

When I uncomment the line of setting figure.title, I get the expected latex result, except that the caption is still empty.
```
\begin{figure}
\centering
\includegraphics{img/logo.png}
\caption{}
\end{figure}
```

So I am confused what is the difference between caption and title, and how can I set the caption.


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