%b:BLOCK% is [a] container
Checks if a block is a container (chest, barrel, hopper, etc.).
if block is a container:
Every distinct way you can write this pattern, with optional groups and choice groups expanded. Placeholders are shown as <name>.
<b> is container
<b> is a container
%b:BLOCK% inventory (is|is not) empty
slot %slot:INT% of %inv:EXPR% is empty
slot %slot:INT% of %inv:EXPR% is not empty
%inv:EXPR% inventory is empty
%inv:EXPR% inventory is not empty
%inv:EXPR% inventory contains %mat:MATERIAL%
%inv:EXPR% inventory does not contain %mat:MATERIAL%
%inv:EXPR% is [a] lumen inventory
%inv:EXPR% is not [a] lumen inventory