code: def _validate_style_keys_pce(styles, conditions, tags):
      """Validate styles dict keys for plot_compare_evokeds."""
      styles = deepcopy(styles)
      if not set(styles).issubset(tags.union(conditions)):
          raise ValueError(
              f'The keys in "styles" ({list(styles)}) must match the keys in '
              f'"evokeds" ({conditions}).'
          )
      # make sure all the keys are in there
      for cond in conditions:
          if cond not in styles:
              styles[cond] = dict()
          # deal with matplotlib's synonymous handling of "c" and "color" /
          # "ls" and "linestyle" / "lw" and "linewidth"
          elif "c" in styles[cond]:
              styles[cond]["color"] = styles[cond].pop("c")
          elif "ls" in styles[cond]:
              styles[cond]["linestyle"] = styles[cond].pop("ls")
          elif "lw" in styles[cond]:
              styles[cond]["linewidth"] = styles[cond].pop("lw")
          # transfer styles from partial-matched entries
          for tag in cond.split("/"):
              if tag in styles:
                  styles[cond].update(styles[tag])
      # remove the (now transferred) partial-matching style entries
      for key in list(styles):
          if key not in conditions:
              del styles[key]
      return styles
  
imports: from copy import deepcopy
  from functools import partial
  from itertools import cycle
  from numbers import Integral
  import numpy
  from .._fiff.pick import _DATA_CH_TYPES_SPLIT, _PICK_TYPES_DATA_DICT, _VALID_CHANNEL_TYPES, _picks_to_idx, channel_indices_by_type, channel_type, pick_info
  from ..defaults import _handle_default
  from ..fixes import _is_last_row
  from ..utils import _check_ch_locs, _check_if_nan, _clean_names, _is_numeric, _pl, _to_rgb, _validate_type, fill_doc, logger, verbose, warn
  from .topo import _plot_evoked_topo
  from .topomap import _check_sphere, _draw_outlines, _get_pos_outlines, _make_head_outlines, _prepare_topomap, _prepare_topomap_plot, _set_contour_locator, plot_topomap
  from .utils import DraggableColorbar, _check_cov, _check_delayed_ssp, _check_option, _check_time_unit, _draw_proj_checkbox, _get_cmap, _get_color_list, _make_combine_callable, _plot_masked_image, _prepare_joint_axes, _process_times, _prop_kw, _set_title_multiple_electrodes, _set_window_title, _setup_ax_spines, _setup_cmap, _setup_plot_projector, _setup_vmin_vmax, _triage_rank_sss, _trim_ticks, _validate_if_list_of_axes, plt_show
label_desc: Use image node_id 21 for calling a global function with example usage: _validate_style_keys_pce(styles, conditions, tags) and returns: styles