def initialize(self):
        """Initialize a connection to the LDAP server.

        :return: LDAP connection object.
        """

        try:
            conn = ldap.initialize('{0}://{1}:{2}'.format(
                current_app.config['LDAP_SCHEMA'],
                current_app.config['LDAP_HOST'],
                current_app.config['LDAP_PORT']))
            conn.set_option(ldap.OPT_NETWORK_TIMEOUT,
                            current_app.config['LDAP_TIMEOUT'])
            conn = self._set_custom_options(conn)
            conn.protocol_version = ldap.VERSION3
            if current_app.config['LDAP_USE_TLS']:
                conn.start_tls_s()
            return conn
        except ldap.LDAPError as e:
            raise LDAPException(self.error(e.args))
Initialize a connection to the LDAP server.

        :return: LDAP connection object.