class_docstr: Branin function (2-dimensional with 3 global minima).
code: def _f(self, X: np.ndarray) -> float:
      x_1 = X[0]
      x_2 = X[1]
      return float(
          (
              x_2
              - 5.1 / (4 * np.pi**2) * x_1**2
              + 5.0 / np.pi * x_1
              - 6.0
          )
          ** 2
          + 10 * (1 - 1.0 / (8 * np.pi)) * np.cos(x_1)
          + 10
      )
  
imports: from abc import ABC, abstractmethod
  from typing import Any, Callable, List, Optional, Tuple, Union
  import numpy
  import torch
  from ax.utils.common.docutils import copy_doc
  from ax.utils.common.typeutils import checked_cast, not_none
  from botorch.test_functions import synthetic
label_desc: Use image node_id 1 for calling the Branin obj's underlying member method code with example usage: obj._f(X) and returns: float