new_contents: 
  import sys 
  
  import tft_ir_api as IR 
  
  var_AA = IR.RealVE("AA", 0, 0.0, 100.0)
  var_BB = IR.RealVE("BB", 1, 0.0, 100.0)
  var_CC = IR.RealVE("CC", 2, 0.0, 100.0)
  
  rel = IR.BE("+", 4, IR.BE("+", 3, var_AA, var_BB), var_CC)
  
  IR.TuneExpr(rel) 
  
  # tft_ir_backend.ExportExpr2ExprsFile(rel, 0.01, "toy0.exprs")
  # tft_ir_backend.ExportCppInsts(9, "toy0.cpp", "../__tft_alloc_text") 
  
subject: update for the first hello world example