code: def plot_quantile_returns_violin(
      return_by_q, ylim_percentiles=None, ax=None
  ):
      """
      Plots a violin box plot of period wise returns for factor quantiles.
  
      Parameters
      ----------
      return_by_q : pd.DataFrame - MultiIndex
          DataFrame with date and quantile as rows MultiIndex,
          forward return windows as columns, returns as values.
      ylim_percentiles : tuple of integers
          Percentiles of observed data to use as y limits for plot.
      ax : matplotlib.Axes, optional
          Axes upon which to plot.
  
      Returns
      -------
      ax : matplotlib.Axes
          The axes that were plotted on.
      """
  
      return_by_q = return_by_q.copy()
  
      if ylim_percentiles is not None:
          ymin = (
              np.nanpercentile(return_by_q.values, ylim_percentiles[0])
              * DECIMAL_TO_BPS
          )
          ymax = (
              np.nanpercentile(return_by_q.values, ylim_percentiles[1])
              * DECIMAL_TO_BPS
          )
      else:
          ymin = None
          ymax = None
  
      if ax is None:
          f, ax = plt.subplots(1, 1, figsize=(18, 6))
  
      unstacked_dr = return_by_q.multiply(DECIMAL_TO_BPS)
      unstacked_dr.columns = unstacked_dr.columns.set_names(
          "forward_periods"
      )
      unstacked_dr = unstacked_dr.stack()
      unstacked_dr.name = "return"
      unstacked_dr = unstacked_dr.reset_index()
  
      sns.violinplot(
          data=unstacked_dr,
          x="factor_quantile",
          hue="forward_periods",
          y="return",
          orient="v",
          cut=0,
          inner="quartile",
          ax=ax,
      )
      ax.set(
          xlabel="",
          ylabel="Return (bps)",
          title="Period Wise Return By Factor Quantile",
          ylim=(ymin, ymax),
      )
  
      ax.axhline(0.0, linestyle="-", color="black", lw=0.7, alpha=0.6)
  
      return ax
  
imports: import numpy
  import pandas
  from scipy import stats
  import statsmodels.api
  import seaborn
  import matplotlib.cm
  import matplotlib.pyplot
  from matplotlib.ticker import ScalarFormatter
  from functools import wraps
  from .None import utils
  from .None import performance
label_desc: Use image node_id 12 for calling a global function with example usage: plot_quantile_returns_violin(return_by_q, ylim_percentiles, ax) and returns: ax