private static StructuralVectorBoolSix GetRestraint(GsaNode gsaNode)
 {
   if (gsaNode.NodeRestraint == NodeRestraint.Custom && gsaNode.Restraints != null && gsaNode.Restraints.Count() > 0)
   {
     return Helper.AxisDirDictToStructuralVectorBoolSix(gsaNode.Restraints);
   }
   else if (gsaNode.NodeRestraint == NodeRestraint.Fix)
   {
     return new StructuralVectorBoolSix(Enumerable.Repeat(true, 6));
   }
   else if (gsaNode.NodeRestraint == NodeRestraint.Pin)
   {
     return new StructuralVectorBoolSix(Enumerable.Repeat(true, 3).Concat(Enumerable.Repeat(false, 3)));
   }
   return null;
 }