code: @Deprecated
  	public static Class<?> getCollectionFieldType(Field collectionField, int nestingLevel, Map<Integer, Integer> typeIndexesPerLevel) {
  		return ResolvableType.forField(collectionField).getNested(nestingLevel, typeIndexesPerLevel).asCollection().resolveGeneric();
  	}
docs: Determine the generic element type of the given Collection field.
  @param collectionField the collection field to introspect
  @param nestingLevel the nesting level of the target type
  (typically 1; e.g. in case of a List of Lists, 1 would indicate the
  nested List, whereas 2 would indicate the element of the nested List)
  @param typeIndexesPerLevel Map keyed by nesting level, with each value
  expressing the type index for traversal at that level
  @return the generic type, or {@code null} if none
  @deprecated as of 4.0, in favor of using {@link ResolvableType} for arbitrary nesting levels