code: def _copy_channel(inst, ch_name, new_ch_name):
      """Add a copy of a channel specified by ch_name.
  
      Input data can be in the form of Raw, Epochs or Evoked.
  
      The instance object is modified inplace.
  
      Parameters
      ----------
      inst : instance of Raw | Epochs | Evoked
          Data containing the EEG channels
      ch_name : str
          Name of the channel to copy.
      new_ch_name : str
          Name given to the copy of the channel.
  
      Returns
      -------
      inst : instance of Raw | Epochs | Evoked
          The data with a copy of a given channel.
      """
      new_inst = inst.copy().pick([ch_name])
      new_inst.rename_channels({ch_name: new_ch_name})
      inst.add_channels([new_inst], force_update_info=True)
      return inst
  
file_path: mne-python/mne/_fiff/reference.py
imports: import numpy
  from ..defaults import DEFAULTS
  from ..fixes import pinv
  from ..utils import _check_option, _check_preload, _on_missing, _validate_type, fill_doc, logger, verbose, warn
  from .constants import FIFF
  from .meas_info import _check_ch_keys
  from .pick import _ELECTRODE_CH_TYPES, pick_channels, pick_channels_forward, pick_types
  from .proj import _has_eeg_average_ref_proj, make_eeg_average_ref_proj, setup_proj
label_desc: Use image node_id 1 for calling a global function with example usage: _copy_channel(inst, ch_name, new_ch_name) and returns: inst