code: def generate_momentum_normal(d, massmatrix):
      """draw direction vector according to mass matrix"""
      return np.random.multivariate_normal(
          np.zeros(d), np.dot(massmatrix, np.eye(d))
      )
  
imports: import numpy
  import matplotlib.pyplot
  import scipy.special
  import scipy.stats
label_desc: Use image node_id 7 for calling a global function with example usage: generate_momentum_normal(d, massmatrix) and returns: np