code: def n_volume(r, n):
      """compute the n-volume of a sphere of radius r in n dimensions"""
      return np.pi ** (0.5 * n) / special.gamma(0.5 * n + 1) * (r**n)
  
file_path: astroML/astroML/density_estimation/density_estimation.py
imports: import numpy
  from scipy import special
  from sklearn.base import BaseEstimator
  from sklearn.neighbors import BallTree
label_desc: Use image node_id 1 for calling a global function with example usage: n_volume(r, n) and returns: unknown