'Lists the identities in a pool.
:type identity_pool_id: string
:param identity_pool_id: An identity pool ID in the format REGION:GUID.
:type max_results: integer
:param max_results: The maximum number of identities to return.
:type next_token: string
:param next_token: A pagination token.'

def list_identities(self, identity_pool_id, max_results, next_token=None):

    params = {'IdentityPoolId': identity_pool_id, 'MaxResults': max_results}
    if (next_token is not None):
        params['NextToken'] = next_token
    return self.make_request(action='ListIdentities', body=json.dumps(params))
