class_docstr: Transformer for assignments from system commands (a = !foo)
class_docstr_tok: ["Transformer","for","assignments","from","system","commands","(","a","=","!","foo",")"]
code: def find_pre_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.ERRORTOKEN)
          ):
              ix = assign_ix + 1
  
              while (
                  ix < len(line)
                  and line[ix].type == tokenize.ERRORTOKEN
              ):
                  if line[ix].string == "!":
                      return cls(line[ix].start)
                  elif not line[ix].string.isspace():
                      break
                  ix += 1
  
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 1 for calling the SystemAssign obj's underlying member method code with example usage: obj.find_pre_312(cls, tokens_by_line) and returns: cls