code: def value_to_string(self, obj):
      return self.get_prep_value(self.value_from_object(obj))
  
imports: from django.contrib.postgres.operations import CreateExtension
  from django.contrib.postgres.indexes import PostgresIndex
  from django.db.models import Field, FloatField, Func, Value
  import numpy
  from .forms import VectorFormField
  from ..utils import from_db, to_db
label_desc: Use image node_id 7 for calling the VectorField obj's underlying member method code with example usage: obj.value_to_string(obj) and returns: self