input: Write a python function to perform basic CRUD operations.
  assert crud.read() == []
  crud.create('record1')
  assert crud.read() == ['record1']
  crud.create('record2')
  assert crud.read() == ['record1', 'record2']
  crud.update(0, 'updated_record1')
  assert crud.read() == ['updated_record1', 'record2']
  crud.delete(1)
  assert crud.read() == ['updated_record1']
output: class CRUD:
      def __init__(self):
          self.records = []
  
      def create(self, record):
          self.records.append(record)
  
      def read(self):
          return self.records
  
      def update(self, index, new_record):
          if 0 <= index < len(self.records):
              self.records[index] = new_record
  
      def delete(self, index):
          if 0 <= index < len(self.records):
              del self.records[index]
  
  crud = CRUD()