mackchainladder doesn't work on multi-triangles

[henrydingliu]

Are you on the latest chainladder version?

• Yes, this bug occurs on the latest version.

Describe the bug in words

Fitting a triangle objective with either multiple index or multiple columns will break mackchainladder

How can the bug be reproduced?

this errors out

tri = cl.load_sample('clrd').loc['Agway Ins Co']['IncurLoss','CumPaidLoss']
cl.MackChainladder().fit(tri)

What is the expected behavior?

this should fit normally

[henrydingliu]

found this while working on summary for mack. will resolve shortly