use of Unique in mySQL field cases Error

I am trying to use this one again in MyModel:
public function insertIgnore(array $data)
{
$_prepared = array();
foreach ($data as $col => $val)
{
$_prepared[$this->db->_escape_identifiers($col)] = $this->db->escape($val);
}
$this->db->query('INSERT IGNORE INTO `exclude_choices` ('.implode(',',array_keys($_prepared)).') VALUES('.implode(',',array_values($_prepared)).');');
}

I modified $_prepared[_escape_identifiers($col)] = escape($val); to get rid of the $this->db. Now I get "call to undefined function _escape_identifiers()".

Any idea?

proof that an old dog can learn new tricks