Reformat code.
Added test for MutableMap.+=
Added test for MutableMap.++=
Added test for MutableMap.-=
Added test for MutableMap.-= collection
Added test for Map.(k)
Added test for Map.contains
Added test for Map.filter
Added test for Map.filterKeys
Added test for Map.get
Added test for Map.getOrElse
Added test for Map.isDefinedAt
Added test for Map.keys
Added test for Map.keysIterator
Added test for Map.keysSet
Added test for Map.mapValues
Added test for Map.values
Added test for Map.valuesIterator