def describe_loa(connectionId=None, providerName=None, loaContentType=None):
    """
    Returns the LOA-CFA for a connection, interconnect, or link aggregation group (LAG).
    The Letter of Authorization - Connecting Facility Assignment (LOA-CFA) is a document that is used when establishing your cross connect to AWS at the colocation facility. For more information, see Requesting Cross Connects at AWS Direct Connect Locations in the AWS Direct Connect user guide.
    See also: AWS API Documentation
    
    
    :example: response = client.describe_loa(
        connectionId='string',
        providerName='string',
        loaContentType='application/pdf'
    )
    
    
    :type connectionId: string
    :param connectionId: [REQUIRED]
            The ID of a connection, LAG, or interconnect for which to get the LOA-CFA information.
            Example: dxcon-abc123 or dxlag-abc123
            Default: None
            

    :type providerName: string
    :param providerName: The name of the service provider who establishes connectivity on your behalf. If you supply this parameter, the LOA-CFA lists the provider name alongside your company name as the requester of the cross connect.
            Default: None
            

    :type loaContentType: string
    :param loaContentType: A standard media type indicating the content type of the LOA-CFA document. Currently, the only supported value is 'application/pdf'.
            Default: application/pdf
            

    :rtype: dict
    :return: {
        'loaContent': b'bytes',
        'loaContentType': 'application/pdf'
    }
    
    
    """
    pass
