docs: def sbessely_array(xvec, N):
      """Outputs an array where each column is a vector of sbessel values. This
      is useful for plotting a set of Spherical Bessel Functions:
  
          A = sbessel.sbessely_array(np.linspace(.1,20,100),40)
          for sb in A:
              plot(sb)
          ylim((-.4,.4))
          show()
      """
  
      first_time = True  
      for x in xvec:
          a = sbessely(x, N)
          if first_time:
              out = np.array([a])
              first_time = False
          else:
              out = np.concatenate([out, [a]], axis=0)
              
      return out.T