How to use the meshio._helpers.reader_map.keys function in meshio

def _get_info_parser():
    parser = argparse.ArgumentParser(
        description=("Print mesh info."), formatter_class=argparse.RawTextHelpFormatter
    )

    parser.add_argument("infile", type=str, help="mesh file to be read from")

    parser.add_argument(
        "--input-format",
        "-i",
        type=str,
        choices=sorted(list(reader_map.keys())),
        help="input file format",
        default=None,
    )

    parser.add_argument(
        "--version",
        "-v",
        action="version",
        version=_get_version_text(),
        help="display version information",
    )
    return parser

def _get_parser():
    parser = argparse.ArgumentParser(
        description=("Compress mesh file."),
        formatter_class=argparse.RawTextHelpFormatter,
    )

    parser.add_argument("infile", type=str, help="mesh file to compress")

    parser.add_argument(
        "--input-format",
        "-i",
        type=str,
        choices=sorted(list(reader_map.keys())),
        help="input file format",
        default=None,
    )

    parser.add_argument(
        "--max", "-max", action="store_true", help="maximum compression", default=False,
    )

    parser.add_argument(
        "--version",
        "-v",
        action="version",
        version=_get_version_text(),
        help="display version information",
    )
    return parser

def _get_parser():
    parser = argparse.ArgumentParser(
        description=("Covert mesh file to binary format."),
        formatter_class=argparse.RawTextHelpFormatter,
    )

    parser.add_argument("infile", type=str, help="mesh file to convert")

    parser.add_argument(
        "--input-format",
        "-i",
        type=str,
        choices=sorted(list(reader_map.keys())),
        help="input file format",
        default=None,
    )

    parser.add_argument(
        "--version",
        "-v",
        action="version",
        version=_get_version_text(),
        help="display version information",
    )
    return parser

def _get_parser():
    parser = argparse.ArgumentParser(
        description=("Decompress mesh file."),
        formatter_class=argparse.RawTextHelpFormatter,
    )

    parser.add_argument("infile", type=str, help="mesh file to decompress")

    parser.add_argument(
        "--input-format",
        "-i",
        type=str,
        choices=sorted(list(reader_map.keys())),
        help="input file format",
        default=None,
    )

    parser.add_argument(
        "--version",
        "-v",
        action="version",
        version=_get_version_text(),
        help="display version information",
    )
    return parser

args_string = self._format_args(action, default)
            return ", ".join(action.option_strings) + " " + args_string

    parser = argparse.ArgumentParser(
        description=("Convert between mesh formats."),
        # formatter_class=argparse.RawTextHelpFormatter,
        formatter_class=CustomHelpFormatter,
    )

    parser.add_argument("infile", type=str, help="mesh file to be read from")

    parser.add_argument(
        "--input-format",
        "-i",
        type=str,
        choices=sorted(list(reader_map.keys())),
        help="input file format",
        default=None,
    )

    parser.add_argument(
        "--output-format",
        "-o",
        type=str,
        choices=sorted(list(_writer_map.keys())),
        help="output file format",
        default=None,
    )

    parser.add_argument(
        "--ascii",
        "-a",

__email__ = "tianyikillua@gmail.com"
__copyright__ = "Copyright (c) 2019 {} <{}>".format(__author__, __email__)
__license__ = "License :: OSI Approved :: MIT License"
__version__ = "0.3.3"
__status__ = "Development Status :: 4 - Beta"

paraview_plugin_version = __version__

if float(meshio.__version__[:3]) < 3.3:
    vtk_to_meshio_type = meshio._vtk.vtk_to_meshio_type
    meshio_to_vtk_type = meshio._vtk.meshio_to_vtk_type
    meshio_input_filetypes = meshio._helpers.input_filetypes
else:
    vtk_to_meshio_type = meshio.vtk._vtk.vtk_to_meshio_type
    meshio_to_vtk_type = meshio.vtk._vtk.meshio_to_vtk_type
    meshio_input_filetypes = list(meshio._helpers.reader_map.keys())
meshio_extensions = [ext[1:] for ext in meshio._helpers._extension_to_filetype.keys()]
meshio_input_filetypes = ["automatic"] + meshio_input_filetypes


@smproxy.reader(
    name="meshio Reader",
    extensions=meshio_extensions,
    file_description="meshio-supported files",
    support_reload=False,
)
class meshioReader(VTKPythonAlgorithmBase):
    def __init__(self):
        VTKPythonAlgorithmBase.__init__(
            self, nInputPorts=0, nOutputPorts=1, outputType="vtkUnstructuredGrid"
        )
        self._filename = None

from paraview.util.vtkAlgorithm import (
    VTKPythonAlgorithmBase,
    smdomain,
    smhint,
    smproperty,
    smproxy,
)
from vtkmodules.numpy_interface import dataset_adapter as dsa
from vtkmodules.vtkCommonDataModel import vtkUnstructuredGrid

import meshio

paraview_plugin_version = meshio.__version__
vtk_to_meshio_type = meshio.vtk._vtk.vtk_to_meshio_type
meshio_to_vtk_type = meshio.vtk._vtk.meshio_to_vtk_type
meshio_input_filetypes = list(meshio._helpers.reader_map.keys())
meshio_extensions = [ext[1:] for ext in meshio.extension_to_filetype.keys()]
meshio_input_filetypes = ["automatic"] + meshio_input_filetypes


@smproxy.reader(
    name="meshio reader",
    extensions=meshio_extensions,
    file_description="meshio-supported files",
    support_reload=False,
)
class MeshioReader(VTKPythonAlgorithmBase):
    def __init__(self):
        VTKPythonAlgorithmBase.__init__(
            self, nInputPorts=0, nOutputPorts=1, outputType="vtkUnstructuredGrid"
        )
        self._filename = None