Submits a list of structures to the Materials Project as SNL files.
        The argument list mirrors the arguments for the StructureNL object,
        except that a list of structures with the same metadata is used as an
        input.

        .. note::

            As of now, this MP REST feature is open only to a select group of
            users. Opening up submissions to all users is being planned for
            the future.

        Args:
            structures: A list of Structure objects
            authors (list): List of {"name":'', "email":''} dicts,
                *list* of Strings as 'John Doe <johndoe@gmail.com>',
                or a single String with commas separating authors
            projects ([str]): List of Strings ['Project A', 'Project B'].
                This applies to all structures.
            references (str): A String in BibTeX format. Again, this applies to
                all structures.
            remarks ([str]): List of Strings ['Remark A', 'Remark B']
            data ([dict]): A list of free form dict. Namespaced at the root
                level with an underscore, e.g. {"_materialsproject":<custom
                data>}. The length of data should be the same as the list of
                structures if not None.
            histories: List of list of dicts - [[{'name':'', 'url':'',
                'description':{}}], ...] The length of histories should be the
                same as the list of structures if not None.
            created_at (datetime): A datetime object

        Returns:
            A list of inserted submission ids.

def submit_structures(self, structures, authors, projects=None,
                          references='', remarks=None, data=None,
                          histories=None, created_at=None):
        """
        Submits a list of structures to the Materials Project as SNL files.
        The argument list mirrors the arguments for the StructureNL object,
        except that a list of structures with the same metadata is used as an
        input.

        .. note::

            As of now, this MP REST feature is open only to a select group of
            users. Opening up submissions to all users is being planned for
            the future.

        Args:
            structures: A list of Structure objects
            authors (list): List of {"name":'', "email":''} dicts,
                *list* of Strings as 'John Doe <johndoe@gmail.com>',
                or a single String with commas separating authors
            projects ([str]): List of Strings ['Project A', 'Project B'].
                This applies to all structures.
            references (str): A String in BibTeX format. Again, this applies to
                all structures.
            remarks ([str]): List of Strings ['Remark A', 'Remark B']
            data ([dict]): A list of free form dict. Namespaced at the root
                level with an underscore, e.g. {"_materialsproject":<custom
                data>}. The length of data should be the same as the list of
                structures if not None.
            histories: List of list of dicts - [[{'name':'', 'url':'',
                'description':{}}], ...] The length of histories should be the
                same as the list of structures if not None.
            created_at (datetime): A datetime object

        Returns:
            A list of inserted submission ids.
        """
        from pymatgen.util.provenance import StructureNL
        snl_list = StructureNL.from_structures(structures, authors, projects,
                                               references, remarks, data,
                                               histories, created_at)
        self.submit_snl(snl_list)