code: def plot_cov_estimators(ax, X, estimators):
      plot_cov_ellipse(ax, C_ref, edgecolor="C0", label="Reference")
      for i, est in enumerate(estimators):
          C = Covariances(estimator=est).transform(X[np.newaxis, ...])[
              0
          ]
          plot_cov_ellipse(ax, C, edgecolor=f"C{i+2}", label=est)
      ax.legend(loc="upper left")
      return ax
  
imports: import numpy
  from matplotlib import pyplot
  from matplotlib.patches import Ellipse
  import matplotlib.transforms
  from pyriemann.estimation import Covariances
label_desc: Use image node_id 2 for calling a global function with example usage: plot_cov_estimators(ax, X, estimators) and returns: ax