This is attribute
gives an estimate of the number of entries that will be stored in the
KeyMap. It is
used to tune the internal properties of the KeyMap for speed and efficiency. A larger
value will result in faster access at the expense of increased memory requirements.
However if the SizeGuess value is much larger than the actual size of the KeyMap, then
there will be little, if any, speed gained by making the SizeGuess even larger. The
default value is 300.
The value of this attribute can only be changed if the KeyMap is empty. Its value can
be set conveniently when creating the KeyMap. An error will be reported if an attempt
is made to set or clear the attribute when the KeyMap contains any entries.