code: def update_pos(self, pos_id, name, pos_type, location=None):
          
          arguments = {'name': name,
                       'type': pos_type,
                       'location': location}
          return self.do_req('PUT',
                             self.merchant_api_base_url + '/pos/' +
                             pos_id + '/', arguments)
docs: Update POS resource. Returns the raw response object.
  
          Arguments:
              pos_id:
                  POS id as chosen on registration
              name:
                  Human-readable name of the POS, used for displaying payment
                  request origin to end user
              pos_type:
                  POS type
              location:
                  Merchant location