code: public function getA(StringType $name)
      {
          if (!$this->hasA($name)) {
              throw new AttributesException("Attribute: {$name} does not exist");
          }
  
          return $this->attributes[$name()];
      }
docs: Get an attribute
  
  @param StringType $name name of attribute
  
  @return Attribute
  
  @throws AttributesException Thrown if named attribute does not exists