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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_organisations(self, service_desk_id=None, start=0, limit=50):
 """ Returns a list of organizations in the Jira instance. If the user is not an agent, the resource returns a list of organizations the user is a member of. :param service_desk_id: OPTIONAL: str Get organizations from single Service Desk :param start: OPTIONAL: int The starting index of the returned objects. Base index: 0. See the Pagination section for more details. :param limit: OPTIONAL: int The maximum number of users to return per page. Default: 50. See the Pagination section for more details. :return: """

        url_without_sd_id = 'rest/servicedeskapi/organization'
        url_with_sd_id = 'rest/servicedeskapi/servicedesk/{}/organization'.format(service_desk_id)
        params = {}
        if start is not None:
            params['start'] = int(start)
        if limit is not None:
            params['limit'] = int(limit)

        if service_desk_id is None:
            return self.get(url_without_sd_id, headers=self.experimental_headers, params=params)
        else:
            return self.get(url_with_sd_id, headers=self.experimental_headers, params=params)