How to reorder the text blocks of a text file with python? : I have a text file like this:

    Label: A
    
    Text1
    
    Text2
    
    Label: B
    
    Text3
    
    Text4
    
    Label: C
    
    Text5
    
    Text6

I would like to reorder the blocks of text in the inverse order, maintaining the original order within the blocks. Like this:

    Label: C
    
    Text5
    
    Text6
    
    Label: B
    
    Text3
    
    Text4
    
    Label: A
    
    Text1
    
    Text2

The line with `Label` always contains the same text, I'm adding here the letters for a better explanation. Also, the `Label` is always at the same position and uses a full line.

The only constrains are: Python 3.6 and no external modules. I can load the full file in memory, so no need for read the file line by line if you don't want.

I know how to find the lines with the `Label` but I don't know how to select the block of text to change the order. Any idea?.