ch8n

// you need to first convert to map 
mutableListOf<Pair<String,Int>>(pair,updatedPair).toMap()
// then you have access to mutableMap extension
mutableListOf<Pair<String,Int>>(pair,updatedPair).toMap().toMutableMap()
//signature
fun <K, V> Map<out K, V>.toMutableMap(): MutableMap<K, V>

ch8n

val pair = "2" to 1
val updatedPair = pair.copy(first = "1")

ch8n

// return old value, if updating existing entry else null
abstract fun put(key: K, value: V): V?
abstract fun putAll(from: Map<out K, V>)
abstract fun clear()
// return removed value, if not existing then null
abstract fun remove(key: K): V?
open fun remove(key: K, value: V): Boolean

ch8n

abstract val entries: MutableSet<MutableEntry<K, V>> is a MutableSet

ch8n

abstract fun setValue(newValue: V): V

ch8n

interface MutableMap<K, V> : Map<K, V>

ch8n

fun <K, V> mapOf(vararg pairs: Pair<K, V>): Map<K, V> 
  = if (pairs.size > 0){
      pairs.toMap(LinkedHashMap(mapCapacity(pairs.size))) 
    }else{ 
      emptyMap()
    }
// Linked HashMap signature
class LinkedHashMap<K, V> : MutableMap<K, V> 
// since MutableMap<K, V> has Map as parent class
// Casting it to map make it immutable* (read-only)

ch8n

fun <K, V> mapOf(pair: Pair<K, V>): Map<K, V> 
  = java.util.Collections.singletonMap(pair.first, pair.second)
// In java.util.Collections, 
public static Map singletonMap(K key, V value) 
//a function that return an immutable map, which is serializable.
//it is mapping only the specified key to the specified value.

ch8n

fun <K, V> mapOf(): Map<K, V> = emptyMap()
// emptyMap is resolved by
object EmptyMap : Map<Any?, Nothing>, Serializable
// which return read-only empty map implementation

ch8n

// Kotlin Standard Library function
fun <K, V> mapOf(): Map<K, V> 
fun <K, V> mapOf(pair: Pair<K, V>): Map<K, V> 
fun <K, V> mapOf(vararg pairs: Pair<K, V>): Map<K, V>