This type represents the Microsoft concept of a Boolean. Accordingly, this
cell represents either TRUE, FALSE or an error condition. This third
state naturally makes handling BooleanCells quite tricky, and use of
the specific access methods should be handled with care
Gets the boolean value stored in this cell. If this cell contains an
error, then returns FALSE. Always query this cell type using the
accessor method isError() prior to calling this method
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TRUE if this cell contains TRUE, FALSE if it contains FALSE or
an error code