code: def entropy(pk, qk=None, base=None):
      pk = astensor(pk)
      pk = 1.0 * pk / mt.sum(pk, axis=0)
      if qk is None:
          vec = mt_special.entr(pk)
      else:
          qk = astensor(qk)
          if len(qk) != len(pk):
              raise ValueError("qk and pk must have same length.")
          qk = 1.0 * qk / mt.sum(qk, axis=0)
          vec = mt_special.rel_entr(pk, qk)
      S = mt.sum(vec, axis=0)
      if base is not None:
          if isinstance(base, TENSOR_TYPE):
              S /= mt.log(base)
          else:
              S /= log(base)
      return S
  
imports: from math import log
  from ...None import tensor
  from ...tensor import special
  from ..core import TENSOR_TYPE
  from ..datasource import tensor
  from ..utils import implement_scipy
label_desc: Use image node_id 1 for calling a global function with example usage: entropy(pk, qk, base) and returns: S