Split PSI file to PSI elements chunks

Hello.

I'm creating my first IntelliJ plugin and I want to get a file content in PSI format so I can read data from it.
The file I'm trying to read is .yml and look something like this:

functions:
  addTodo:
    handler: src/addTodo.handler
    events:
      - httpApi:
          path: /
          method: post
  fetchTodos:
    handler: src/fetchTodos.handler
    events:
      - httpApi:
          path: /todos
          method: get
  fetcTodo:
    handler: src/fetchTodo.handler
    events:
      - httpApi:
          path: /todo/{id}
          method: get
  updateTodo:
    handler: src/updateTodo.handler
    events:
      - httpApi:
          path: /todo/{id}
          method: put

I would like to get all functions names and know their row number. So far I was only able to get the all files as text using the PsiManager.

PsiManager.getInstance(project).findFile(file);

How can I get the function names and row number?