Describe the bug
First of all, thanks for this very nice plugin. There are two issues, probably related:

1. Output is only generated with print, not by calling the variable/object.

   This will produce nothing:
   '''python exec="on" source="material-block"
   x=1
   x
   '''

   This will work:
   '''python exec="on" source="material-block"
   x=1
   print(x)
   '''
   1

2. Line breaks are not respected.

   This will print the two numbers next to each other, rather than below each other.
   '''python exec="on" source="material-block"
   x=1
   y=1
   print(x)
   print(y)
   '''
   1 2

Expected behavior
I would expect the output to be as in the console, so that the code examples are representative of real use.

System (please complete the following information):

• Markdown Exec version: 1.6.0
• Python version: e.g. 3.10
• OS: Windows