code: def _single_convert_output(self, expr):
      return expr
  
imports: import json
  import math
  import numpy
  from m2cgen import ast
  from m2cgen.assemblers import utils
  from m2cgen.assemblers.base import ModelAssembler
  from m2cgen.assemblers.linear import _linear_to_ast
label_desc: Use image node_id 9 for calling the BaseBoostingAssembler obj's underlying member method code with example usage: obj._single_convert_output(expr) and returns: expr