code: def rpc_get_account_at(self, address, block_height, **con_info):
          
          if not check_account_address(address):
              return {'error': 'Invalid address', 'http_status': 400}
  
          if not check_block(block_height):
              return {'error': 'Invalid start block', 'http_status': 400}
  
          # must be b58
          if is_c32_address(address):
              address = c32ToB58(address)
      
          db = get_db_state(self.working_dir)
          account_states = db.get_account_at(address, block_height)
          db.close()
  
          # return credit_value and debit_value as strings, so the unwitting JS developer doesn't get confused
          # as to why large balances get mysteriously converted to doubles.
          ret = [self.export_account_state(hist) for hist in account_states]
          return self.success_response({'history': ret})
docs: Get the account's statuses at a particular block height.
          Returns the sequence of history states on success