abstract contract ERC165 is IERC165 {
	/*
	 * bytes4(keccak256('supportsInterface(bytes4)')) == 0x01ffc9a7
	 */
	bytes4 private constant _INTERFACE_ID_ERC165 = 0x01ffc9a7;

	/**
	 * @dev Mapping of interface ids to whether or not it's supported.
	 */
	mapping(bytes4 => bool) private _supportedInterfaces;

	constructor () internal {
		// Derived contracts need only register support for their own interfaces,
		// we register support for ERC165 itself here
		_registerInterface(_INTERFACE_ID_ERC165);
	}

	/**
	 * @dev See {IERC165-supportsInterface}.
	 *
	 * Time complexity O(1), guaranteed to always use less than 30 000 gas.
	 */
	function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
		return _supportedInterfaces[interfaceId];
	}

	/**
	 * @dev Registers the contract as an implementer of the interface defined by
	 * `interfaceId`. Support of the actual ERC165 interface is automatic and
	 * registering its interface id is not required.
	 *
	 * See {IERC165-supportsInterface}.
	 *
	 * Requirements:
	 *
	 * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
	 */
	function _registerInterface(bytes4 interfaceId) internal virtual {
		require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
		_supportedInterfaces[interfaceId] = true;
	}
}
function _registerInterface(bytes4 interfaceId) internal virtual {
	require(interfaceId != 0xffffffff, "ERC165: invalid interface id");
	_supportedInterfaces[interfaceId] = true;
}

/**
 	 * @dev Registers the contract as an implementer of the interface defined by
 	 * `interfaceId`. Support of the actual ERC165 interface is automatic and
 	 * registering its interface id is not required.
 	 *
 	 * See {IERC165-supportsInterface}.
 	 *
 	 * Requirements:
 	 *
 	 * - `interfaceId` cannot be the ERC165 invalid interface (`0xffffffff`).
 	 */