code: def _simulate_stsp(self, x: np.ndarray) -> float:
      order = np.argsort(x)
      self.order = order
      x = self.x[order]
      y = self.y[order]
      output = np.sqrt((x[0] - x[-1]) ** 2 + (y[0] - y[-1]) ** 2) + sum(
          np.sqrt((x[i] - x[i + 1]) ** 2 + (y[i] - y[i + 1]) ** 2)
          for i in range(self.dimension - 1)
      )
      if self.complex:
          output += np.sum(np.diff(order) ** 2) / np.sqrt(
              self.dimension + 1.0
          )
      return float(output)
  
file_path: nevergrad/nevergrad/functions/stsp/core.py
imports: import matplotlib.pyplot
  import numpy
  from nevergrad.parametrization import parameter
  from ..base import ExperimentFunction
label_desc: Use image node_id 2 for calling the STSP obj's underlying member method code with example usage: obj._simulate_stsp(x) and returns: float