code: def _element_keywords(cls, backend, elements=None):
          "Returns a dictionary of element names to allowed keywords"
          if backend not in Store.loaded_backends():
              return {}
  
          mapping = {}
          backend_options = Store.options(backend)
          elements = elements if elements is not None else backend_options.keys()
          for element in elements:
              if '.' in element: continue
              element = element if isinstance(element, tuple) else (element,)
              element_keywords = []
              options = backend_options['.'.join(element)]
              for group in Options._option_groups:
                  element_keywords.extend(options[group].allowed_keywords)
  
              mapping[element[0]] = element_keywords
          return mappinf _element_keywords(cls, backend, elements=None):
          "Returns a dictionary of element names to allowed keywords"
          if backend not in Store.loaded_backends():
              return {}
  
          mapping = {}
          backend_options = Store.options(backend)
          elements = elements if elements is not None else backend_options.keys()
          for element in elements:
              if '.' in element: continue
              element = element if isinstance(element, tuple) else (element,)
              element_keywords = []
              options = backend_options['.'.join(element)]
              for group in Options._option_groups:
                  element_keywords.extend(options[group].allowed_keywords)
  
              mapping[element[0]] = element_keywords
          return mapping
docs: Returns a dictionary of element names to allowed keywords