code: def find_group_vals(df, group_cols):
      group_vals, _ = retrieve_chart_data(df, group_cols)
      group_vals = group_vals.drop_duplicates().sort_values(group_cols)
      group_f, _ = build_formatters(group_vals, nan_display="NaN")
      return group_f.format_dicts(group_vals.itertuples())
  
imports: import copy
  import numpy
  import pandas
  import dtale.global_state
  import dtale.pandas_util
  from dtale.column_analysis import handle_cleaners
  from dtale.constants import CHART_JOINER_CHAR
  from dtale.query import build_col_key, run_query
  from dtale.utils import ChartBuildingError, build_formatters, classify_type, find_dtype, find_dtype_formatter, flatten_lists, get_dtypes, json_int, make_list, triple_quote
label_desc: Use image node_id 18 for calling a global function with example usage: find_group_vals(df, group_cols) and returns: group_f