docs: def to_dict(self, files=None):
          """
          Converts the CodeBaseDoc into a dictionary containing the to_dict()
          representations of each contained file.  The optional `files` list
          lets you restrict the dict to include only specific files.
  
          >>> CodeBaseDoc(['examples']).to_dict(['class.js']).get('module.js')
          >>> CodeBaseDoc(['examples']).to_dict(['class.js'])['class.js'][0]['name']
          'MyClass'
  
          """
          keys = files or list(self.keys())
          return dict((key, self[key].to_dict()) for key in keys)