code: def warmup_shell(ndim):
      radius = 0.1
      ctr = 0.5
      # choose radial distance inside shell
      length = 0.4 + np.random.uniform(-radius, radius)
  
      # choose direction
      x = ctr + random_vector(ndim, length=length)
      return x
  
imports: import numpy
  from math import gamma, pi, exp
label_desc: Use image node_id 22 for calling a global function with example usage: warmup_shell(ndim) and returns: x