def extract_matching_pattern(regex, group_name, unfiltered_list):
    """
        Return the desired group_name from a list of matching patterns

        @param regex : a regular expression with named groups
        @param group_name : the desired matching group name value
        @param unfiltered_list : a list of matches
        
        @rtype : the string value
    """
    result = ''
    filtered_list = list(filter(regex.search, unfiltered_list))
    
    if len(filtered_list) == 1:
        filtered_string = ''.join(filtered_list)
        result = regex.search(filtered_string).group(group_name)
    
    return result