class_docstr: Transformer for assignments from system commands (a = !foo)
class_docstr_tok: ["Transformer","for","assignments","from","system","commands","(","a","=","!","foo",")"]
code: def find_post_312(cls, tokens_by_line):
      for line in tokens_by_line:
          assign_ix = _find_assign_op(line)
          if (
              (assign_ix is not None)
              and not line[assign_ix].line.strip().startswith("=")
              and (len(line) >= assign_ix + 2)
              and (line[assign_ix + 1].type == tokenize.OP)
              and (line[assign_ix + 1].string == "!")
          ):
              return cls(line[assign_ix + 1].start)
  
imports: import ast
  from codeop import CommandCompiler, Compile
  import re
  import sys
  import tokenize
  from typing import List, Tuple, Optional, Any
  import warnings
  from IPython.utils import tokenutil
label_desc: Use image node_id 2 for calling the SystemAssign obj's underlying member method code with example usage: obj.find_post_312(cls, tokens_by_line) and returns: cls