code: def add_showcases(self, showcases, showcases_to_check=None):
          # type: (List[Union[hdx.data.showcase.Showcase,Dict,str]], List[hdx.data.showcase.Showcase]) -> bool
          
          if showcases_to_check is None:
              showcases_to_check = self.get_showcases()
          allshowcasesadded = True
          for showcase in showcases:
              if not self.add_showcase(showcase, showcases_to_check=showcases_to_check):
                  allshowcasesadded = False
          return allshowcasesadded
docs: Add dataset to multiple showcases
  
          Args:
              showcases (List[Union[Showcase,Dict,str]]): A list of either showcase ids or showcase metadata from Showcase objects or dictionaries
              showcases_to_check (List[Showcase]): list of showcases against which to check existence of showcase. Defaults to showcases containing dataset.
  
          Returns:
              bool: True if all showcases added or False if any already present