<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def getContacts(self, **kwargs):
 """Returns a list of all contacts. Optional Parameters: * limit -- Limits the number of returned contacts to the specified quantity. Type: Integer Default: 100 * offset -- Offset for listing (requires limit.) Type: Integer Default: 0 Returned structure: [ 'id' : <Integer> Contact identifier 'name' : <String> Contact name 'email' : <String> Contact email 'cellphone' : <String> Contact telephone 'countryiso' : <String> Cellphone country ISO code 'defaultsmsprovider' : <String> Default SMS provider 'directtwitter' : <Boolean> Send Tweets as direct messages 'twitteruser' : <String> Twitter username 'paused' : <Boolean> True if contact is pasued 'iphonetokens' : <String list> iPhone tokens 'androidtokens' : <String list> android tokens ] """


        # Warn user about unhandled parameters
        for key in kwargs:
            if key not in ['limit', 'offset']:
                sys.stderr.write("'%s'" % key + ' is not a valid argument ' +
                                 'of getContacts()\n')

        return [PingdomContact(self, x) for x in
                self.request("GET", "notification_contacts", kwargs).json()['contacts']]