code: def _assemble_estimators(self, trees, split_idx):
      if self._tree_limit:
          trees = trees[: self._tree_limit]
  
      return [self._assemble_tree(t) for t in trees]
  
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 2 for calling the BaseTreeBoostingAssembler obj's underlying member method code with example usage: obj._assemble_estimators(trees, split_idx) and returns: unknown