Data analysis wit Excel / R / STATA / PYTHON etc. --- very simple

Freelancer needed for simple data processing task.

In the attached excel file, there are two columns: investor_id and portfolio_company_id.

I want an excel sheet that lists all possible pairs between portfolio_company_id for the same investor_id. That is, first group by investor_id, then create a list of all possible pairs of portfolio_company_id.

Here is an example, assume the following data structure:

investor_id portfolio_company_id
a a1
a a2
b b1
b b2
b b3

Then, I am looking for an output file as follows:
investor_id portfolio_company_id1 portfolio_company_id2
a a1 a2
b b1 b2
b b1 b3
b b2 b3

The data is attached. The job should be done within 24 hours. Budget is 30 USD.

Thanks!