Obsersable subscribe been called twice

I would like to execute subscribe only once. Here is my code

let usuario_senha = this.usuario + "_" + this.senha;
    let subscription = this.afoDatabase.list('usuarios/', {query: {
      orderByChild: 'usuario_senha',
      equalTo: usuario_senha
    }}).take(1).subscribe((x) => {
      if(x.length == 1)
      {
        console.log("true");
      }
      else
      {
        console.log("false");
    }},
    error =>{
        console.error("Error in subscribe: ", error.message);
    },
    () =>{
      console.log("done");
    });

it prints “false”/“true” and “done” 2x each time it is called.

[SOLVED] https://stackoverflow.com/questions/48486542/rxjs-subscribe-been-called-twice