Custom world generation/rule test


 * The root tag
 * : Can be, for a random chance that depends on a block's distance to the structure's origin ,  to test for a block,  to test for specific block states,  to test for a block with a random chance or  to test for a block in a block tag.
 * If is :
 * : Can be, or
 * : The chance for the predicate to pass when the distance of a block to the structure's origin is equal to.
 * : The chance for the predicate to pass when the distance of a block to the structure's origin is equal to . If a block's distance is between  and, chance is obtained by  between the values of  and.
 * If is :
 * : A block ID.
 * If is :
 * : ID of the block
 * : Block states
 * : A block state key and its value.
 * If is :
 * : A block ID.
 * : The probability (between 0 and 1) of the predicate to pass if the block is found.
 * If is :
 * : The namespaced ID of a block tag
 * : The probability (between 0 and 1) of the predicate to pass if the block is found.
 * If is :
 * : The namespaced ID of a block tag