code: def _single_convert_output(self, expr):
      supported_objectives = {
          "cross_entropy": ast.SigmoidExpr,
          "cross_entropy_lambda": self._log1p_exp_transform,
          "regression": self._maybe_sqr_transform,
          "regression_l1": self._maybe_sqr_transform,
          "huber": super()._single_convert_output,
          "fair": self._maybe_sqr_transform,
          "poisson": self._exp_transform,
          "quantile": self._maybe_sqr_transform,
          "mape": self._maybe_sqr_transform,
          "gamma": self._exp_transform,
          "tweedie": self._exp_transform,
          "custom": super()._single_convert_output,
      }
      if self.objective_name not in supported_objectives:
          raise ValueError(
              f"Unsupported objective function '{self.objective_name}'"
          )
      return supported_objectives[self.objective_name](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 7 for calling the LightGBMModelAssembler obj's underlying member method code with example usage: obj._single_convert_output(expr) and returns: supported_objectives