Parse the root XML element as a dictionary.

def parse_at_root(
            self,
            root,  # type: ET.Element
            state  # type: _ProcessorState
    ):
        # type: (...) -> Any
        """Parse the root XML element as a dictionary."""
        parsed_dict = {}  # type: Dict

        dict_element = _element_find_from_root(root, self.element_path)
        if dict_element is not None:
            parsed_dict = self.parse_at_element(dict_element, state)
        elif self.required:
            raise MissingValue('Missing required root aggregate "{}"'.format(self.element_path))

        return parsed_dict