class_docstr: Base class for a vertex.
class_docstr_tok: ["Base","class","for","a","vertex","."]
code: def __getattr__(self, item):
      if item not in ["x_a"]:
          raise AttributeError(
              f"{type(self)} object has no attribute " f"'{item}'"
          )
      if item == "x_a":
          self.x_a = np.array(self.x)
          return self.x_a
  
imports: import collections
  from abc import ABC, abstractmethod
  import numpy
  from scipy._lib._util import MapWrapper
label_desc: Use image node_id 3 for calling the VertexBase obj's underlying member method code with example usage: obj.__getattr__(item) and returns: self