code: public SDVariable log(String name, SDVariable in, double base) {
          validateNumerical("log", in);
          SDVariable ret = f().log(in, base);
          return updateVariableNameAndReference(ret, name);
      }
docs: Element-wise logarithm function (with specified base): out = log_{base}(x)
  
  @param name Name of the output variable
  @param in   Input variable
  @param base Logarithm base
  @return Output variable