def prune_distribution_formats(formats):
    """derive a unique list of distribution formats"""
    counter = 0
    formats_ = []
    unique_formats = []
    for k1, v1 in formats.items():
        row = {}
        for k2, v2 in v1.items():
            if k2.startswith('format'):
                row[k2] = v2
        formats_.append(row)
    num_elements = len(formats)
    for f in range(0, len(formats_)):
        counter += 1
        if formats_[f] not in unique_formats:
            unique_formats.append(formats_[f])
        if num_elements == counter:
            break
    return unique_formats
