class_docstr: Implementation of Magics command line parser.
class_docstr_tok: ["Implementation","of","Magics","command","line","parser","."]
docstr: Parses the commandline and returns ParsedArgs and post-processing tokens.
  
  Args:
    line: The line to parse (usually contents from cell Magics).
    placeholders: Placeholders from prompts in the cell contents.
  
  Returns:
    A tuple of (parsed_args, post_processing_tokens).
docstr_tok: ["Parses","the","commandline","and","returns","ParsedArgs","and","post-processing","tokens",".","Args",":","line",":","The","line","to","parse","(","usually","contents","from","cell","Magics",")",".","placeholders",":","Placeholders","from","prompts","in","the","cell","contents",".","Returns",":","A","tuple","of","(","parsed_args",",","post_processing_tokens",")","."]
code: def parse_line(
      self,
      line: str,
      placeholders: AbstractSet[str] | None = None,
  ) -> tuple[
      parsed_args_lib.ParsedArgs, parsed_args_lib.PostProcessingTokens
  ]:
      """Parses the commandline and returns ParsedArgs and post-processing tokens.
  
      Args:
        line: The line to parse (usually contents from cell Magics).
        placeholders: Placeholders from prompts in the cell contents.
  
      Returns:
        A tuple of (parsed_args, post_processing_tokens).
      """
      tokens, post_processing_tokens = CmdLineParser._tokenize_line(
          line
      )
  
      parsed_args = self._get_parsed_args_from_cmd_line_tokens(
          tokens=tokens, placeholders=placeholders
      )
  
      # Special-case for "compare" command: because the prompts are compiled into
      # the left- and right-hand side functions rather than in the cell body, we
      # cannot examine the cell body to get the placeholders.
      #
      # Instead we parse the command line twice: once to get the left- and right-
      # functions, then we query the functions for their placeholders, then
      # parse the commandline again to validate the inputs.
      if parsed_args.cmd == parsed_args_lib.CommandName.COMPARE_CMD:
          assert parsed_args.lhs_name_and_fn is not None
          assert parsed_args.rhs_name_and_fn is not None
          _, lhs_fn = parsed_args.lhs_name_and_fn
          _, rhs_fn = parsed_args.rhs_name_and_fn
          parsed_args = self._get_parsed_args_from_cmd_line_tokens(
              tokens=tokens,
              placeholders=frozenset(lhs_fn.get_placeholders()).union(
                  rhs_fn.get_placeholders()
              ),
          )
  
      _validate_parsed_args(parsed_args)
  
      for expr in post_processing_tokens:
          post_process_utils.validate_one_post_processing_expression(
              expr
          )
  
      return parsed_args, post_processing_tokens
  
imports: from __future__ import annotations
  import argparse
  import shlex
  import sys
  from typing import AbstractSet, Any, Callable, MutableMapping, Sequence
  from google.generativeai.notebook import argument_parser
  from google.generativeai.notebook import flag_def
  from google.generativeai.notebook import input_utils
  from google.generativeai.notebook import model_registry
  from google.generativeai.notebook import output_utils
  from google.generativeai.notebook import parsed_args_lib
  from google.generativeai.notebook import post_process_utils
  from google.generativeai.notebook import py_utils
  from google.generativeai.notebook import sheets_utils
  from google.generativeai.notebook.lib import llm_function
  from google.generativeai.notebook.lib import llmfn_inputs_source
  from google.generativeai.notebook.lib import llmfn_outputs
  from google.generativeai.notebook.lib import model
label_desc: Use image node_id 4 for calling the CmdLineParser obj's underlying member method code with example usage: obj.parse_line(line, placeholders) and returns: parsed_args,  post_processing_tokens