Overrides \Drupal\block\BlockBase::blockForm().
Overrides BlockBase::blockForm
public function blockForm($form, &$form_state) {
$form['block_count'] = array(
'#type' => 'select',
'#title' => t('Number of news items in block'),
'#default_value' => $this->configuration['block_count'],
'#options' => drupal_map_assoc(range(2, 20)),
);
return $form;
}