Fix pylint issues

With #50 done we will have a running pipeline for API and frontend. For introducing the pipeline in the bginning I disabled all pylint issues we had with the code (see pyproject.toml for disabled problems).

To have a clean code each warning need to be removed from the list disable and need to be fixed except wrong-import-order. Issues we have (check if fixed):

• missing-module-docstring
• missing-function-docstring
• missing-class-docstring
• consider-using-f-string
• invalid-name
• too-many-arguments
• redefined-builtin
• missing-timeout
• raise-missing-from
• redefined-outer-name
• bare-except
• unused-variable
• duplicate-code
• line-too-long
• unused-argument
• unnecessary-negation
• unused-import
• too-many-lines
• no-else-return
• pointless-statement