How to use the pelican.signals.content_object_init function in pelican

def register():
    signals.initialized.connect(init)
    try:
        signals.all_generators_finalized.connect(run_plugin)
    except AttributeError:
        # NOTE: This may result in #314 so shouldn't really be relied on
        # https://github.com/getpelican/pelican-plugins/issues/314
        signals.content_object_init.connect(clean_summary)

def register():
    signals.content_object_init.connect(content_object_init)

def register():
    signals.content_object_init.connect(override_metadata)
    signals.page_generator_finalized.connect(set_relationships)

def register():
    """
    Part of Pelican API
    """
    signals.content_object_init.connect(content_object_init)

def register():
    signals.content_object_init.connect(embed_tweet)

def register():
    signals.initialized.connect(init_default_config)
    signals.content_object_init.connect(bootstrapify)

def register():
    signals.initialized.connect(init_default_config)
    signals.content_object_init.connect(generate_toc)

def register():
    signals.initialized.connect(initialized)
    signals.get_generators.connect(generator.get_generators)
    signals.content_object_init.connect(content.update_content)
    signals.finalized.connect(thumbnails.generate_thumbnails)

def register(): # for Pelican
    import pelican.signals

    pelican.signals.initialized.connect(_pelican_configure)
    pelican.signals.content_object_init.connect(new_page)

def register():
    signals.content_object_init.connect(_handle_content_object_init)
    signals.article_generator_finalized.connect(_inject_aggregates)