def get_property_content(content, prefix):
    """Add the prefix to each object in the content and return the
    concatenated string with "," as the separator.
    Args:
        content: the list containing property objects
        prefix: the prefix before dcid, such as "dcs:"
    Returns:
        objects separated by comma. For example:
        "dcs:bio/CWH41_YEAST,dcs:bio/RPN3_YEAST"
    """
    if not content:
        return None
    item_list = []
    for obj in content:
        item_list.append(prefix + obj)
    return ','.join(item_list)