Make all functions view and virtual to allow them to overriden more freely

Author: bbenligiray

contracts/Api3PartialAggregatorV2V3Interface.sol

@@ -33,7 +33,13 @@ contract Api3PartialAggregatorV2V3Interface is AggregatorV2V3Interface {
     /// @dev AggregatorV2V3Interface users are already responsible with
     /// validating the values that they receive (e.g., revert if the spot price
     /// of an asset is negative). Therefore, this contract omits validation.
-    function latestAnswer() external view override returns (int256 value) {
+    function latestAnswer()
+        external
+        view
+        virtual
+        override
+        returns (int256 value)
+    {
         (value, ) = IProxy(api3Proxy).read();
     }
 
@@ -46,42 +52,51 @@ contract Api3PartialAggregatorV2V3Interface is AggregatorV2V3Interface {
     function latestTimestamp()
         external
         view
+        virtual
         override
         returns (uint256 timestamp)
     {
         (, timestamp) = IProxy(api3Proxy).read();
     }
 
     /// @dev API3 feeds are updated asynchronously and not in rounds.
-    function latestRound() external pure override returns (uint256) {
+    function latestRound() external view virtual override returns (uint256) {
         revert FunctionIsNotSupported();
     }
 
     /// @dev Functions that use the round ID as an argument are not supported.
-    function getAnswer(uint256) external pure override returns (int256) {
+    function getAnswer(
+        uint256
+    ) external view virtual override returns (int256) {
         revert FunctionIsNotSupported();
     }
 
     /// @dev Functions that use the round ID as an argument are not supported.
-    function getTimestamp(uint256) external pure returns (uint256) {
+    function getTimestamp(uint256) external view virtual returns (uint256) {
         revert FunctionIsNotSupported();
     }
 
     /// @dev API3 feeds always use 18 decimals.
-    function decimals() external pure override returns (uint8) {
+    function decimals() external view virtual override returns (uint8) {
         return 18;
     }
 
     /// @dev The deterministic proxy address acts as the description, and this
     /// is left empty to save gas on contract deployment.
-    function description() external pure override returns (string memory) {
+    function description()
+        external
+        view
+        virtual
+        override
+        returns (string memory)
+    {
         return "";
     }
 
     /// @dev A unique version is chosen to easily check if an unverified
     /// contract that acts as a Chainlink feed is an
     /// Api3PartialAggregatorV2V3Interface.
-    function version() external pure override returns (uint256) {
+    function version() external view virtual override returns (uint256) {
         return 4913;
     }
 
@@ -90,7 +105,8 @@ contract Api3PartialAggregatorV2V3Interface is AggregatorV2V3Interface {
         uint80
     )
         external
-        pure
+        view
+        virtual
         override
         returns (uint80, int256, uint256, uint256, uint80)
     {
@@ -103,6 +119,7 @@ contract Api3PartialAggregatorV2V3Interface is AggregatorV2V3Interface {
     function latestRoundData()
         external
         view
+        virtual
         override
         returns (
             uint80 roundId,