input: 
  def create_basic_blockchain() -> 'Blockchain':
      """
      Create a basic blockchain in Python using only the core modules.
      
      Example:
      >>> blockchain = create_basic_blockchain()
      >>> blockchain.create_block(5, '0')
      {'block_number': 1, 'timestamp': blockchain._current_timestamp(), 'nonce': 5, 'previous_hash': '0'}
      """
      import hashlib
      import json
      import time
  
      class Blockchain:
  
          def __init__(self):
              self.chain = []
              self.transactions = []
  
          def create_block(self, nonce, previous_hash):
              block = {
                  'block_number': len(self.chain) + 1,
                  'timestamp': self._current_timestamp(),
                  'nonce': nonce,
                  'previous_hash': previous_hash
              }
              self.chain.append(block)
              return block
  
          def _current_timestamp(self):
              return round(time.time() * 1000)
  
          def hash_block(self, block):
              string_object = json.dumps(block, sort_keys=True)
              block_string = string_object.encode()
              raw_hash = hashlib.sha256(block_string)
              hex_hash = raw_hash.hexdigest()
              return hex_hash
  
      return Blockchain()
  
output:     blockchain = create_basic_blockchain()
      return blockchain