code: def _prepare_xi(self, xi):
      if not self._is_initialized:
          return super()._prepare_xi(xi)
      else:
          # just give back precomputed values
          return (
              self.xi,
              self.xi_shape,
              self.ndim,
              self.nans,
              self.out_of_bounds,
          )
  
imports: import numpy
  from .common import run_monitored, set_mem_rlimit, Benchmark, safe_import
label_desc: Use image node_id 2 for calling the RegularGridInterpolatorValues obj's underlying member method code with example usage: obj._prepare_xi(xi) and returns: super, self,  self,  self,  self,  self