code: def set_legend(ax):
      """
      Set legend on the chart.
  
      Parameters
      ----------
      ax
  
      """
      ax.legend(loc="upper left", ncol=1, fontsize=10, numpoints=1)
  
file_path: catalyst/catalyst/exchange/utils/live_chart_utils.py
imports: import matplotlib.dates
  import pandas
  from catalyst.exchange.exchange_errors import MismatchingQuoteCurrenciesExchanges
label_desc: Use image node_id 2 for calling a global function with example usage: set_legend(ax) without return types