Null-LS: mypy import error(lxml) even tho installation was succussful

Hey Guys,
So im using null-ls (yeah will be archived but fingers crossed or soemthing). Anyway im trying to get mypy running.
I install it via mason. And somehow when i open up a python file i get the following error message.

[null-ls] failed to run generator: ...y/null-ls.nvim/lua/null-ls/helpers/generator_factory.lua:220: error in generator output: You must install the lxml package before you can run mypy with `--cobertura-xml-report`.                     
You can do this with `python3 -m pip install lxml`.                                                                                                                                                                                         
Traceback (most recent call last):                                                                                                                                                                                                          
  File "/home/eisbergsalat/.local/share/nvim/mason/bin/mypy", line 8, in <module>                                                                                                                                                           
    sys.exit(console_entry())                                                                                                                                                                                                               
  File "/home/eisbergsalat/.local/share/nvim/mason/packages/mypy/venv/lib/python3.10/site-packages/mypy/__main__.py", line 15, in console_entry                                                                                             
    main()                                                                                                                                                                                                                                  
  File "mypy/main.py", line 95, in main                                                                                                                                                                                                     
  File "mypy/main.py", line 174, in run_build                                                                                                                                                                                               
  File "mypy/build.py", line 197, in build                                                                                                                                                                                                  
  File "mypy/build.py", line 237, in _build                                                                                                                                                                                                 
  File "mypy/report.py", line 60, in __init__                                                                                                                                                                                               
  File "mypy/report.py", line 77, in add_report                                                                                                                                                                                             
ImportError          

How do i fix this?
How do i install lxml on that venv?