def get_rb_blob_attribute(blobdict, attr):
    """Get Attribute `attr` from dict `blobdict`

    Parameters
    ----------
    blobdict : dict
        Blob Description Dictionary
    attr : string
        Attribute key

    Returns
    -------
    ret : Attribute Value
    """
    try:
        value = blobdict['BLOB']['@' + attr]
    except KeyError:
        raise KeyError('Attribute @' + attr + ' is missing from Blob.' +
                       'There may be some problems with your file')

    return value