code: def unescape_code_start(source, ext, language="python"):
      """Unescape code start"""
      parser = StringParser(language)
      for pos, line in enumerate(source):
          if not parser.is_quoted() and is_escaped_code_start(
              line, ext
          ):
              unescaped = unesc(line, language)
              # don't remove comment char if we break the code start...
              if is_escaped_code_start(unescaped, ext):
                  source[pos] = unescaped
          parser.read_line(line)
      return source
  
file_path: jupytext/src/jupytext/magics.py
imports: import re
  from .languages import _COMMENT, _SCRIPT_EXTENSIONS, usual_language_name
  from .stringparser import StringParser
label_desc: Use image node_id 9 for calling a global function with example usage: unescape_code_start(source, ext, language) and returns: source