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function add_image_insert_override( $sizes ){
unset( $sizes[ 'thumbnail' ]);
unset( $sizes[ 'medium' ]);
unset( $sizes[ 'medium_large' ] );
unset( $sizes[ 'large' ]);
unset( $sizes[ 'full' ] );
return $sizes;
}
add_filter( 'intermediate_image_sizes_advanced', 'add_image_insert_override' );
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add_filter('intermediate_image_sizes_advanced', '__return_empty_array');