code: def optional(name, default) -> 'Wildcard':
          
          return Wildcard(min_count=1, fixed_size=True, variable_name=name, optional=default)
docs: Create a `Wildcard` that matches a single argument with a default value.
  
          If the wildcard does not match, the substitution will contain the
          default value instead.
  
          Args:
              name:
                  The name for the wildcard.
              default:
                  The default value of the wildcard.
  
          Returns:
              A n optional wildcard.