class_docstr: Simple quadratic fitness function which can be used with dimension up to 4
code: def __call__(self, x: tp.ArrayLike) -> float:
      assert len(self.x0) == len(x)
      return float(
          np.sum(
              self.x1 * np.cos(np.array(x, copy=False) - self.x0) ** 2
          )
      )
  
file_path: nevergrad/nevergrad/optimization/test_special.py
imports: import os
  import numpy
  import pytest
  import nevergrad.common.typing
  from .None import test_optimizerlib
  from .None import optimizerlib
  import nevergrad
label_desc: Use image node_id 2 for calling the SimpleFitness obj's underlying member method code with example usage: obj.__call__(x) and returns: float