docstr: Save workbook to disk.
docstr_tok: ["Save","workbook","to","disk","."]
code: def _save(self) -> None:
      """
      Save workbook to disk.
      """
      self.book.save(self._handles.handle)
      if "r+" in self._mode and not isinstance(
          self._handles.handle, mmap.mmap
      ):
          # truncate file to the written content
          self._handles.handle.truncate()
  
imports: from __future__ import annotations
  import mmap
  from typing import TYPE_CHECKING, Any, Tuple, cast
  import numpy
  from pandas._typing import FilePath, ReadBuffer, Scalar, StorageOptions, WriteExcelBuffer
  from pandas.compat._optional import import_optional_dependency
  from pandas.util._decorators import doc
  from pandas.core.shared_docs import _shared_docs
  from pandas.io.excel._base import BaseExcelReader, ExcelWriter
  from pandas.io.excel._util import combine_kwargs, validate_freeze_panes
label_desc: Use image node_id 4 for calling the OpenpyxlWriter obj's underlying member method code with example usage: obj._save() without return types