code: def parse_all(self, sources, path, package_name, root_dir):
          
          filtered = _filter_validate(path, 'sources', sources,
                                      self._sources_validate)
          nodes = itertools.chain.from_iterable(
              self.parse_source_entry(source, path, package_name, root_dir)
              for source in filtered
          )
  
          for node_type, node in nodes:
              yield node_type, node
docs: Parse all the model dictionaries in sources.
  
          :param List[dict] sources: The `sources` section of the schema.yml, as
              a list of dicts.
          :param str path: The path to the schema.yml file
          :param str package_name: The name of the current package
          :param str root_dir: The root directory of the search