Convert caffe model definition into Symbol

    Parameters
    ----------
    prototxt_fname : str
        Filename of the prototxt file

    Returns
    -------
    Symbol
        Converted Symbol
    tuple
        Input shape

def convert_symbol(prototxt_fname):
    """Convert caffe model definition into Symbol

    Parameters
    ----------
    prototxt_fname : str
        Filename of the prototxt file

    Returns
    -------
    Symbol
        Converted Symbol
    tuple
        Input shape
    """
    sym, output_name, input_dim = _parse_proto(prototxt_fname)
    exec(sym)                   # pylint: disable=exec-used
    _locals = locals()
    exec("ret = " + output_name, globals(), _locals)  # pylint: disable=exec-used
    ret = _locals['ret']
    return ret, input_dim