docstr: Returns a new PandasMmtf object with the dataframes subset to the
  given model index.
  
  Parameters
  ----------
  model_indices : List[int]
      A list representing the model indexes to subset to.
  
  Returns
  ---------
  pandas_pdb.PandasMmtf : A new PandasPdb object
      containing the structure subsetted to the given model.
code: def get_models(self, model_indices: List[int]) -> PandasMmtf:
      """Returns a new PandasMmtf object with the dataframes subset to the
      given model index.
  
      Parameters
      ----------
      model_indices : List[int]
          A list representing the model indexes to subset to.
  
      Returns
      ---------
      pandas_pdb.PandasMmtf : A new PandasPdb object
          containing the structure subsetted to the given model.
      """
  
      df = copy.deepcopy(self)
  
      if "ATOM" in df.df.keys():
          df.df["ATOM"] = df.df["ATOM"].loc[
              [
                  x in model_indices
                  for x in df.df["ATOM"]["model_id"].tolist()
              ]
          ]
      if "HETATM" in df.df.keys():
          df.df["HETATM"] = df.df["HETATM"].loc[
              [
                  x in model_indices
                  for x in df.df["HETATM"]["model_id"].tolist()
              ]
          ]
      if "ANISOU" in df.df.keys():
          df.df["ANISOU"] = df.df["ANISOU"].loc[
              [
                  x in model_indices
                  for x in df.df["ANISOU"]["model_id"].tolist()
              ]
          ]
      return df
  
imports: from __future__ import annotations
  import os
  import copy
  import gzip
  import warnings
  from string import ascii_uppercase
  from typing import Any, Dict, List, Union
  from warnings import warn
  import numpy
  import pandas
  from looseversion import LooseVersion
  from mmtf import MMTFDecoder, MMTFEncoder, fetch, parse, parse_gzip
  from biopandas.constants import protein_letters_3to1_extended
  from ..pdb.engines import amino3to1dict, pdb_df_columns, pdb_records
label_desc: Use image node_id 22 for calling the PandasMmtf obj's underlying member method code with example usage: obj.get_models(model_indices) and returns: df