Compare only the content of the documents (ignoring the meta fields).

def compare_content(self, other):
        '''
        Compare only the content of the documents (ignoring the meta fields).
        '''
        if type(self) is not type(other):
            return False
        s1 = self.snapshot()
        s2 = other.snapshot()
        for snapshot in (s1, s2):
            for key in snapshot.keys():
                if key[0] in ('_', '.'):
                    del snapshot[key]
        return s1 == s2