code: def sphere(x: np.ndarray) -> float:
      """The most classical continuous optimization testbed.
  
      If you do not solve that one then you have a bug."""
      assert x.ndim == 1
      return float(x.dot(x))
  
imports: from math import exp, sqrt, tanh
  import numpy
  import nevergrad.common.typing
  from nevergrad.common.decorators import Registry
label_desc: Use image node_id 2 for calling a global function with example usage: sphere(x) and returns: float