code: function(query) {
      var result = true; 
      this.each(function() {
        if(!SpahQL.assert(query, this.sourceData(), this.value(), this.path())) {
          result = false;
          return false;
        }
      });
      return result;
    }
docs: SpahQL#assert(query) -> Boolean
  
  Runs an assertion query against every item in this set. Returns <code>false</code> if any one item fails to meet the assertion.
  
  select("/foo/foo").first().assert("/foo") // Is exactly the same as just asserting /foo/foo/foo.