code: def build_col_def(freq, col="date"):
      return "{}{}{}".format(col, CHART_JOINER_CHAR, freq)
  
file_path: dtale/tests/dtale/test_charts.py
imports: import pandas
  import pytest
  import dtale.charts.utils
  from dtale.constants import CHART_JOINER_CHAR
label_desc: Use image node_id 1 for calling a global function with example usage: build_col_def(freq, col) and returns: str