Add missing import

Author: mtfishman

src/treetensornetworks/opsum_to_ttn/opsum_to_ttn.jl

@@ -3,7 +3,7 @@
 using Graphs: degree, is_tree
 using ITensors: flux, has_fermion_string, itensor, removeqns, space
 using ITensors.LazyApply: Prod, Sum, coefficient
-using ITensors.NDTensors: Block, blockdim, maxdim, nblocks, nnzblocks
+using ITensors.NDTensors: Block, blockdim, maxdim, nblocks, nnzblocks, truncate!
 using ITensors.Ops: argument, coefficient, Op, OpSum, name, params, site, terms, which_op
 using NamedGraphs.GraphsExtensions:
   GraphsExtensions, boundary_edges, degrees, is_leaf_vertex, vertex_path