The index.d.ts file in React contains an interface definition that includes the following code snippet. Can you explain the significance of the third line shown below?
(props: P & { children?: ReactNode }, context?: any): ReactElement<any> | null;type SFC<P = {}> = StatelessComponent<P>;
interface StatelessComponent<P = {}> {
(props: P & { children?: ReactNode }, context?: any): ReactElement<any> | null;
propTypes?: ValidationMap<P>;
contextTypes?: ValidationMap<any>;
defaultProps?: Partial<P>;
displayName?: string;
}