code: def _remove_special(label: Hashable) -> str:
      """Remove special characters from label."""
      return "".join(
          [item for item in str(label) if item.isalnum() or "_" in item]
      )
  
file_path: pyjanitor/janitor/functions/clean_names.py
imports: import unicodedata
  from typing import Hashable, Optional, Union
  import pandas
  import pandas_flavor
  from pandas.api.types import is_scalar
  from janitor.errors import JanitorError
  from janitor.functions.utils import _is_str_or_cat, get_index_labels
  from janitor.utils import deprecated_alias
label_desc: Use image node_id 4 for calling a global function with example usage: _remove_special(label) and returns: str