class_docstr: Introspect UDF bytecode and determine if we can rewrite as native expression.
class_docstr_tok: ["Introspect","UDF","bytecode","and","determine","if","we","can","rewrite","as","native","expression","."]
docstr: Translate postfix bytecode instructions to polars expression/string.
code: def to_expression(self, col: str) -> str | None:
      """Translate postfix bytecode instructions to polars expression/string."""
      self._map_target_name = None
      if self._param_name is None:
          return None
  
      # decompose bytecode into logical 'and'/'or' expression blocks (if present)
      control_flow_blocks = defaultdict(list)
      logical_instructions = []
      jump_offset = 0
      for idx, inst in enumerate(self._rewritten_instructions):
          if inst.opname in OpNames.CONTROL_FLOW:
              jump_offset = self._rewritten_instructions[idx + 1].offset
              logical_instructions.append(inst)
          else:
              control_flow_blocks[jump_offset].append(inst)
  
      # convert each block to a polars expression string
      caller_variables: dict[str, Any] = {}
      try:
          expression_strings = self._inject_nesting(
              {
                  offset: InstructionTranslator(
                      instructions=ops,
                      caller_variables=caller_variables,
                      map_target=self._map_target,
                  ).to_expression(
                      col=col,
                      param_name=self._param_name,
                      depth=int(bool(logical_instructions)),
                  )
                  for offset, ops in control_flow_blocks.items()
              },
              logical_instructions,
          )
      except NotImplementedError:
          return None
      polars_expr = " ".join(
          expr for _offset, expr in expression_strings
      )
  
      # note: if no 'pl.col' in the expression, it likely represents a compound
      # constant value (e.g. `lambda x: CONST + 123`), so we don't want to warn
      if "pl.col(" not in polars_expr:
          return None
      elif self._map_target == "series":
          target_name = self._get_target_name(col, polars_expr)
          return polars_expr.replace(f'pl.col("{col}")', target_name)
      else:
          return polars_expr
  
imports: from __future__ import annotations
  import datetime
  import dis
  import inspect
  import re
  import sys
  import warnings
  from bisect import bisect_left
  from collections import defaultdict
  from dis import get_instructions
  from inspect import signature
  from itertools import count, zip_longest
  from pathlib import Path
  from typing import TYPE_CHECKING, AbstractSet, Any, Callable, ClassVar, Iterator, Literal, NamedTuple, Union
label_desc: Use image node_id 12 for calling the BytecodeParser obj's underlying member method code with example usage: obj.to_expression(col) and returns: None, None, None, polars_expr, polars_expr