code: def __getitem__(self, x, nn=None):
      try:
          return self.cache[x]
      except KeyError:
          self.index += 1
          xval = self.Vertex(
              x,
              field=self.field,
              nn=nn,
              index=self.index,
              field_args=self.field_args,
              g_cons=self.g_cons,
              g_cons_args=self.g_cons_args,
          )
  
          self.cache[x] = xval  # Define in cache
          self.gpool.add(xval)  # Add to pool for processing feasibility
          self.fpool.add(
              xval
          )  # Add to pool for processing field values
          return self.cache[x]
  
imports: import collections
  from abc import ABC, abstractmethod
  import numpy
  from scipy._lib._util import MapWrapper
label_desc: Use image node_id 2 for calling the VertexCacheField obj's underlying member method code with example usage: obj.__getitem__(x, nn) and returns: self, self