varOnlyUsedHere = () => {
      return workspace.getVariableUsesById(currId).every((block) => {
        return (
          block.id == sourceBlock.id ||
          (block.getProcedureCall &&
            block.getProcedureCall() == sourceBlock.getProcedureDef()[0])
        );
      });
    }
Returns true if the variable associated with this field is only used
by this block, or callers of this procedure.
@returns {boolean} True if the variable associated with this field is
    only used by this block, or callers of this procedure.