DICTIONARY.contains
Checks if an element with the given key exists in the dictionary.
Syntax
contains( key STRING )
   RETURNS BOOLEAN
- key is the dictionary key to check.
 
Usage
The contains() method scans the dictionary to find if there is an element with
the key passed as parameter.
The method returns TRUE if the element exists, or FALSE if the
element is not found.
Example
MAIN
    DEFINE dict DICTIONARY OF STRING
    LET dict["abc"] = 111
    LET dict["def"] = 222
    LET dict["xyz"] = 999
    DISPLAY dict.contains("def") -- shows 1 (TRUE)
    DISPLAY dict.contains("zzz") -- shows 0 (FALSE)
END MAIN