def Id(id):
    """
    A criterion used to search for records by id. For example
    
    * search for a case by its id
    * search for an alert by its id

    Arguments:
        id (str): the id's value

    Returns:
        dict: JSON repsentation of the criterion
            ```python
            # Query to search for as case by id
            query = Id('1234545643')
            ```
            produces
            ```json
            {
                "_id": "1234545643"
            }
            ```
    """
    return {'_id': id}