def __len__(self):
        """ Number of citation schemes covered by the object

        :rtype: int
        :returns: Number of nested citations
        """
        return len(self.children) + sum([len(child) for child in self.children])
def __len__ ( self ) : return len ( self . children ) + sum ( [ len ( child ) for child in self . children ] )
Number of citation schemes covered by the object

        :rtype: int
        :returns: Number of nested citations