i am new to Azure DevOps and have been trying to run a simple task in azure-pipelines.yml CI pipeline.

```
- stage: Test
  jobs:
  - job: Pytest
    displayName: Pytest
    pool:
      vmImage: ($vmImageName)
    steps:
    - task: UsePythonVersion@0
      inputs:
        versionSpec: '3.8'
    - bash: pytest
    - bash: find ./tests/ -type f -name "*.py" | xargs pylint --jobs=2

```

However, i get the error for the task UsePythonVersion and also for Bash :

A task is missing. The pipeline references a task called 'UsePythonVersion'. This usually indicates the task isn't installed, and you may be able to install it from the Marketplace: <https://marketplace.visualstudio.com>. (Task version 0, job 'Pytest', step ''.)

A task is missing. The pipeline references a task called 'Bash'. This usually indicates the task isn't installed, and you may be able to install it from the Marketplace: <https://marketplace.visualstudio.com>. (Task version 0, job 'Pytest', step ''.)

I tried looking for these on the Marketplace as well, but no clue.
Any leads here would be helpful