def get_reverse_comp(string):
    """Get reverse compliment of a string
    """
    comp_dict = {
        'A': 'T',
        'T': 'A',
        'G': 'C',
        'C': 'G',
        'N': 'N',
    }
    for char in set(string):
        if char not in ['A', 'C', 'G', 'T', 'N']:
            raise ValueError('Not allowed char in string')
            
    new_string = ''.join([comp_dict[char] for char in string[::-1]])
    return new_string