src/Type/SchemaDirectivesList.php
public function addDirective(DirectiveInterface $directive)
    {
        $directiveName = $this->getDirectiveName($directive);
        if ($this->isDirectiveNameRegistered($directiveName)) return $this;

        $this->directivesList[$directiveName] = $directive;

        return $this;
    }
public function addDirective(DirectiveInterface $directive)
    {
        $directiveName = $this->getDirectiveName($directive);
        if ($this->isDirectiveNameRegistered($directiveName)) return $this;

        $this->directivesList[$directiveName] = $directive;

        return $this;
    }
@param DirectiveInterface $directive

@return $this