def ngrammer(s, n):
    """Splits sequence into n-grams

    Parameters:
       s (string): sequence of amino acid
       n (int): number of character in n-gram
    """
    ngram = []                                                                                
    i = 0                                                                                     
    if len(s) < 1:                                                                            
        return []                                                                             
    while i < len(s) - n + 1:                                                                 
        ngram.append(s[i: i + n])                                                             
        i += 1

    return ngram