Add typing overload to improve type validation

Context

• When developing the new analyses, we wanted to avoid having to check whether the return type was dataframe or a list

What was done

• Add more precise function description (see https://docs.python.org/3.9/library/typing.html#typing.overload)

TODO

• /

QA

• code was not unit tested
• acceptance tests were not written

Review objectives

• assessment of code functionality
• assessment of code quality