':param i: a row in *M*
:type i: user or item id
:param n: number of similar elements
:type n: int
:returns: the most similar elements of *i*'

def similar(self, i, n=10):

    if ((not self.get_matrix_similarity()) or (self.get_matrix_similarity().get() is None)):
        self.compute()
    return self._get_row_similarity(i).top_items(n)
