title: MutableLiveData<Pair<Float, Float>>() -> Val cannot be reassigned
body: <p>In my ViewModel in Android project:</p>
  
  <pre><code>import android.app.Application
  import androidx.lifecycle.AndroidViewModel
  import androidx.lifecycle.LiveData
  import androidx.lifecycle.MutableLiveData
  
  class MainViewModel(application: Application) : AndroidViewModel(application) {
      private var waitressCallContainerHeights = MutableLiveData&lt;Pair&lt;Int, Int&gt;&gt;()
  
      fun init() {
             waitressCallContainerHeights.value.first = 200
      }
  }
  </code></pre>
  
  <p>But I get compile error in this line:</p>
  
  <pre><code>       waitressCallContainerHeights.value.first = 200
  
  Val cannot be reassigned
  </code></pre>
  
  <p>I want to set <strong>first</strong> and <strong>second</strong> values in fun <code>init</code></p>