code: def spherical_yn(n, z, derivative=False):
      r"""Spherical Bessel function of the second kind or its derivative.
  
      Defined as [1]_,
  
      .. math:: y_n(z) = \sqrt{\frac{\pi}{2z}} Y_{n + 1/2}(z),
  
      where :math:`Y_n` is the Bessel function of the second kind.
  
      Parameters
      ----------
      n : int, array_like
          Order of the Bessel function (n >= 0).
      z : complex or float, array_like
          Argument of the Bessel function.
      derivative : bool, optional
          If True, the value of the derivative (rather than the function
          itself) is returned.
  
      Returns
      -------
      yn : ndarray
  
      Notes
      -----
      For real arguments, the function is computed using the ascending
      recurrence [2]_.  For complex arguments, the definitional relation to
      the cylindrical Bessel function of the second kind is used.
  
      The derivative is computed using the relations [3]_,
  
      .. math::
          y_n' = y_{n-1} - \frac{n + 1}{z} y_n.
  
          y_0' = -y_1
  
  
      .. versionadded:: 0.18.0
  
      References
      ----------
      .. [1] https://dlmf.nist.gov/10.47.E4
      .. [2] https://dlmf.nist.gov/10.51.E1
      .. [3] https://dlmf.nist.gov/10.51.E2
      """
      if derivative:
          return _spherical_yn_d(n, z)
      else:
          return _spherical_yn(n, z)
  
imports: from __future__ import division, print_function, absolute_import
  from ._ufuncs import _spherical_jn, _spherical_yn, _spherical_in, _spherical_kn, _spherical_jn_d, _spherical_yn_d, _spherical_in_d, _spherical_kn_d
label_desc: Use image node_id 2 for calling a global function with example usage: spherical_yn(n, z, derivative) and returns: _spherical_yn_d, _spherical_yn