def statistics(input_dict):
    """
    Statistics of Annotated Document Corpus.

    :param adc: Annotated Document Corpus.
    :return doc_count (int): Number of Documents.
    :return feature_count (int): Number of Features.
    :return description (string): Statistics.
    """
    output_dict = {}
    output_dict['doc_count'] = len(input_dict['adc'].documents)
    output_dict['feature_count'] = len(input_dict['adc'].features)
    output_dict['description'] = 'Number of documents is ' + str(output_dict
        ['doc_count']) + ', number of corpus features is ' + str(output_dict
        ['feature_count']) + '.'
    return output_dict
