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function isContract(address account) internal view returns (bool);
function sendValue(address payable recipient, uint256 amount) internal;
function functionCall(address target, bytes memory data) internal returns (bytes memory);
function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory);
function functionCallWithValue(address target, bytes memory data, uint256 value) internal returns (bytes memory);
function functionCallWithValue(address target, bytes memory data, uint256 value, string memory errorMessage)
internal
returns (bytes memory);
function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage)
private
returns (bytes memory);
function functionStaticCall(address target, bytes memory data) internal view returns (bytes memory);
function functionStaticCall(address target, bytes memory data, string memory errorMessage)
internal
view
returns (bytes memory);
function functionDelegateCall(address target, bytes memory data) internal returns (bytes memory);
function functionDelegateCall(address target, bytes memory data, string memory errorMessage)
internal
returns (bytes memory);
function _verifyCallResult(bool success, bytes memory returndata, string memory errorMessage)
private
pure
returns (bytes memory);
function addressToString(address _address) internal pure returns (string memory);