code: def _parse_variable_defaults(cls, defaults):
          
  
          default_dict = {}
  
          for item in defaults:
              key = next(iter(item))
              value = item[key]
  
              if key in default_dict:
                  raise RecipeFileInvalid("Default variable value specified twice", name=key, old_value=default_dict[key], new_value=value)
  
              default_dict[key] = value
  
          return default_dict
docs: Parse out all of the variable defaults.