'Convert string to lowercase'

def __string_to_lowercase__(self):

    if self.route_distinguisher:
        self.route_distinguisher = self.route_distinguisher.lower()
    if self.vpn_target_export:
        for (index, ele) in enumerate(self.vpn_target_export):
            self.vpn_target_export[index] = ele.lower()
    if self.vpn_target_import:
        for (index, ele) in enumerate(self.vpn_target_import):
            self.vpn_target_import[index] = ele.lower()
    if self.vpn_target_both:
        for (index, ele) in enumerate(self.vpn_target_both):
            self.vpn_target_both[index] = ele.lower()
