Not able to add `dataSource` to existing subgraph

Question

I am new to GraphQL & The Graph protocol. I have an exisitng subgraph with already 2 dataSource and deployed. Now I want to add 1 more new dataSource to subgraph. According to The Graph docs, I ran below commands:

npx graph add <contract address>
npx graph codegen && npx graph build

But after running npx graph codegen && npx graph build, I am getting this error:

Compile subgraphERROR TS2339: Property 'src' does not exist on type '~lib/@graphprotocol/graph-ts/common/collections/TypedMap<~lib/string/String,~lib/@graphprotocol/graph-ts/common/value/Value>'.

   entity.src = event.params.src
          ~~~
 in src/contract.ts(42,10)

ERROR TS2339: Property 'dst' does not exist on type '~lib/@graphprotocol/graph-ts/common/collections/TypedMap<~lib/string/String,~lib/@graphprotocol/graph-ts/common/value/Value>'.

   entity.dst = event.params.dst
          ~~~
 in src/contract.ts(43,10)

ERROR TS2339: Property 'wad' does not exist on type '~lib/@graphprotocol/graph-ts/common/collections/TypedMap<~lib/string/String,~lib/@graphprotocol/graph-ts/common/value/Value>'.

   entity.wad = event.params.wad
          ~~~
 in src/contract.ts(44,10)

✖ Failed to compile subgraph: Failed to compile data source mapping: 3 compile error(s)
Error: Failed to compile data source mapping: 3 compile error(s)
    at Compiler._compileDataSourceMapping (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@graphprotocol/graph-cli/dist/compiler/index.js:297:19)
    at /home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@graphprotocol/graph-cli/dist/compiler/index.js:201:167
    at updateInDeeply (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/immutable/dist/immutable.js:2121:22)
    at updateInDeeply (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/immutable/dist/immutable.js:2134:23)
    at updateInDeeply (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/immutable/dist/immutable.js:2134:23)
    at updateIn$1 (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/immutable/dist/immutable.js:2099:24)
    at Map.updateIn (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/immutable/dist/immutable.js:2180:12)
    at /home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@graphprotocol/graph-cli/dist/compiler/index.js:201:115
    at /home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/immutable/dist/immutable.js:3321:30
    at List.withMutations (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/immutable/dist/immutable.js:2367:5)
Error: EEXIT: 1
    at Object.exit (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@oclif/core/lib/errors/index.js:21:11)
    at BuildCommand.exit (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@oclif/core/lib/command.js:131:23)
    at BuildCommand.run (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@graphprotocol/graph-cli/dist/commands/build.js:76:22)
    at async BuildCommand._run (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@oclif/core/lib/command.js:117:22)
    at async Config.runCommand (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@oclif/core/lib/config/config.js:329:25)
    at async Object.run (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@oclif/core/lib/main.js:89:16)
Error: The AssemblyScript compiler crashed when compiling this file: 'src/contract.ts'
Suggestion: try to comment the whole file and uncomment it little by little while re-running the graph-cli until you isolate the line where the problem happens.
Also, please contact us so we can make the CLI better by handling errors like this. You can reach out in any of these links:
- Discord channel: https://discord.gg/eM8CA6WA9r
- Github issues: https://github.com/graphprotocol/graph-tooling/issues/new/choose
    at process.<anonymous> (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@graphprotocol/graph-cli/dist/compiler/asc.js:29:11)
    at process.emit (node:events:525:35)
    at processEmit [as emit] (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/signal-exit/index.js:191:37)
    at process.exit (node:internal/process/per_thread:190:15)
    at Object.handle (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@oclif/core/lib/errors/handle.js:33:21)
    at module.exports (/home/rishabh/Documents/freelancing/tax-chain-client-demo/subgraph/taxchain-govt/node_modules/@oclif/core/handle.js:1:58)

May anyone knows what I am doing wrong here? What is the cause of this error and how to resolve it?

I have a delivery deadline tomorrow. Your's answer will really help me to delivery on time.

Thanks in advance.