Calculates the information content of a GO term.

def get_info_content(go_id, termcounts):
    '''
        Calculates the information content of a GO term.
    '''
    # Get the observed frequency of the GO term
    freq = termcounts.get_term_freq(go_id)

    # Calculate the information content (i.e., -log("freq of GO term")
    return -1.0 * math.log(freq) if freq else 0