Hi,

I use the latest version of the AutoMPO to construct a four-body fermion term like C*i+1^{\dag}C*i^{\dag}C*jC*j+1 but I encounter an error message as followings:

*Invalid input to AutoMPO (two strings in a row?)*

Is there any restriction in constructing a general two-body interaction using latest AutoMPO? Thank you.