Is there a Python package to convert InChi to molecular structures?
Yes, RDKit can be used, however, if you installed it with conda it will not work out of the box for inChi key fetching. You can either spend some time installing the missing bit or use something else. It is not like Mol2 support in RDKit, which shouldn't be used, it is just not worth the bother.

I would suggest PubChem's RESTFul API.

Say 

 import requests
 ethanol = 'LFQSCWFLJHTTHZ-UHFFFAOYSA-N'
 r = requests.get(f'https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/inchikey/{ethanol}/property/CanonicalSMILES/JSON').json()
 smiles = r['PropertyTable']['Properties'][0]['CanonicalSMILES']