class_docstr: Price 4 objective function.
  
  This class defines the Price 4 [1]_ global optimization problem. This
  is a multimodal minimization problem defined as follows:
  
  .. math::
  
      f_{\text{Price04}}(x) = (2 x_1^3 x_2 - x_2^3)^2
      + (6 x_1 - x_2^2 + x_2)^2
  
  with :math:`x_i \in [-50, 50]` for :math:`i = 1, 2`.
  
  *Global optimum*: :math:`f(x) = 0` for :math:`x = [0, 0]`,
  :math:`x = [2, 4]` and :math:`x = [1.464, -2.506]`
  
  .. [1] Price, W. A controlled random search procedure for global
  optimisation Computer Journal, 1977, 20, 367-370
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code: def fun(self, x, *args):
      self.nfev += 1
  
      return (2.0 * x[1] * x[0] ** 3.0 - x[1] ** 3.0) ** 2.0 + (
          6.0 * x[0] - x[1] ** 2.0 + x[1]
      ) ** 2.0
  
imports: from numpy import abs, sum, sin, cos, sqrt, log, prod, where, pi, exp, arange, floor, log10, atleast_2d, zeros
  from .go_benchmark import Benchmark
label_desc: Use image node_id 2 for calling the Price04 obj's underlying member method code with example usage: obj.fun(x) and returns: unknown