Function the_posts_navigation() on child theme

Hello,

I am trying to use the plugin WP-PageNavi (https://www.ads-software.com/plugins/wp-pagenavi/) to customise the page navigation links.

To use it, I have to replace the calls to next_posts_link() and previous_posts_link(). In Gazette, they are located in the file \inc\template-tags.php (function the_posts_navigation()).

From what I learnt from this thread (https://www.ads-software.com/support/topic/post-navigation-background-images?replies=6), the_posts_navigation() is a “pluggable” function (it is enclosed by if ( ! function_exists( 'the_posts_navigation' ) ) :).

So I tried to simply copy the function the_posts_navigation() to my child theme and replace the necessary lines in order to use WP-PageNavi. “Since the_posts_navigation() is a pluggable function,” I thought, “I won’t have to do anything else”.

Unfortunately, I was wrong. It’s not working.

I use the plugin Code Snippets (https://www.ads-software.com/plugins/code-snippets/) to manage my custom snippets, and when I try to activate the snippet below…

function the_posts_navigation() {
	// Don't print empty markup if there's only one page.
	if ( $GLOBALS['wp_query']->max_num_pages < 2 ) {
		return;
	}
	?>
	<nav class="navigation posts-navigation" role="navigation">
		<h2 class="screen-reader-text"><?php _e( 'Posts navigation', 'gazette' ); ?></h2>
		<div class="nav-links">

			<?php if ( get_next_posts_link() ) : ?>
			<?php wp_pagenavi(); ?>
			<?php endif; ?>

			<?php if ( get_previous_posts_link() ) : ?>
			<?php wp_pagenavi(); ?>
			<?php endif; ?>

		</div><!-- .nav-links -->
	</nav><!-- .navigation -->
	<?php
}

I get this error:

The code snippet you are trying to save produced a fatal error on line 22:
Cannot redeclare the_posts_navigation() (previously declared in /home/[redacted]/public_html/wp-includes/link-template.php:2462)

What should I do to customise the_posts_navigation() on my child theme so I can use WP-PageNavi?

Thanks again!