```\n        uint locked = \_getAndUpdateLockedAmount(from);\n        if (locked > 0) {\n            require(\_balances[from] >= locked.add(amount), "Token should be unlocked for burning");\n        }\n//-------------------------------------------------------------------------\n\n        \_callTokensToSend(\n            operator, from, address(0), amount, data, operatorData\n        );\n\n        // Update state variables\n        \_totalSupply = \_totalSupply.sub(amount);\n        \_balances[from] = \_balances[from].sub(amount);\n```\n