Remove leading empty lines - #11718

Thanks looks good to me.
I'm still going to ask thoughts of @takluyver who wrote most of this.

Thanks, other than the point about testing, this looks OK to me.

I understand the interest of being able to paste code into a notebook cell and run it without having to fix the indentation, but there are also some downside to this kind of hack:

1. A Python beginner might think that such indentation is valid syntax.
2. If I copy such cell content that runs fine in a notebook and than paste it somewhere else, I will get a syntax error, which can again be confusing to a beginner, and frustrating to a non-beginner.

I don't think its a good idea that a notebook cell be allowed to run Python code with invalid indentation.

If there is really a need to tolerate superfluous indentation when pasting, the indentation should be corrected automatically during the paste process so that if the cell runs without error, it's because the cell contains valid Python syntax.

And such automatic correction behavior should ideally be optional.

Just my 2c.

Happy to make it optional, but someone would have to send patches to IPython/IPykernel to have the relevant configuration hooks.