Determines the number of children in a container #GVariant instance.
This includes variants, maybes, arrays, tuples and dictionary
entries. It is an error to call this function on any other type of
#GVariant.
For variants, the return value is always 1. For values with maybe
types, it is always zero or one. For arrays, it is the length of the
array. For tuples it is the number of tuple items (which depends
only on the type). For dictionary entries, it is always 2
Determines the number of children in a container #GVariant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of #GVariant.
For variants, the return value is always 1. For values with maybe types, it is always zero or one. For arrays, it is the length of the array. For tuples it is the number of tuple items (which depends only on the type). For dictionary entries, it is always 2
This function is O(1).
Return: the number of children in the container