arrange erc721 && erc1155

contracts/external/utils/Context.sol

@@ -0,0 +1,25 @@
+// This is a file copied from https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/utils/Context.sol
+// SPDX-License-Identifier: MIT
+
+pragma solidity 0.6.9;
+
+/*
+ * @dev Provides information about the current execution context, including the
+ * sender of the transaction and its data. While these are generally available
+ * via msg.sender and msg.data, they should not be accessed in such a direct
+ * manner, since when dealing with meta-transactions the account sending and
+ * paying for execution may not be the actual sender (as far as an application
+ * is concerned).
+ *
+ * This contract is only required for intermediate, library-like contracts.
+ */
+abstract contract Context {
+    function _msgSender() internal view virtual returns (address) {
+        return msg.sender;
+    }
+
+    function _msgData() internal view virtual returns (bytes calldata) {
+        this; // silence state mutability warning without generating bytecode - see https://github.com/ethereum/solidity/issues/2691
+        return msg.data;
+    }
+}