code: def from_structures(cls, structures, authors, projects=None,
                          references='', remarks=None, data=None,
                          histories=None, created_at=None):
          
          data = [{}] * len(structures) if data is None else data
          histories = [[]] * len(structures) if histories is None else \
              histories
  
          snl_list = []
          for i, struct in enumerate(structures):
              snl = StructureNL(struct, authors, projects=projects,
                                references=references,
                                remarks=remarks, data=data[i],
                                history=histories[i],
                                created_at=created_at)
              snl_list.append(snl)
  
          return snl_list
docs: A convenience method for getting a list of StructureNL objects by
          specifying structures and metadata separately. Some of the metadata
          is applied to all of the structures for ease of use.
  
          Args:
              structures: A list of Structure objects
              authors: *List* of {"name":'', "email":''} dicts,
                  *list* of Strings as 'John Doe <johndoe@gmail.com>',
                  or a single String with commas separating authors
              projects: List of Strings ['Project A', 'Project B']. This
                  applies to all structures.
              references: A String in BibTeX format. Again, this applies to all
                  structures.
              remarks: List of Strings ['Remark A', 'Remark B']
              data: 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: A datetime object