class_docstr: A ledger to keep track of transactions that occur in the order
  management system.
code: def __init__(self):
      self.transactions: "List[Transaction]" = []
  
imports: from typing import List
  from collections import namedtuple
  import pandas
label_desc: Use image node_id 1 to create a new Ledger object  with example: obj = Ledger()