I try to obtain the connected posets with n elements having a top and bottom such that in the Hasse quiver, in every point there start at most two arrows and at every point there end at most two arrows (thus for example all distributive lattices are of this form). Is there a quick command to obtain this as a list? What condition does one has to add in posets = [ p for p in Posets(n) if p.is_connected() and p.has_top() and p.has_bottom()] ?