Gets the equivalent numpy data type
    for a given nd4j data type.
    # Arguments:
        nd4j_dtype : Nd4j data type. One of
        ['double', 'float', 'half']

def get_np_dtype(nd4j_dtype):
    """
    Gets the equivalent numpy data type
    for a given nd4j data type.
    # Arguments:
        nd4j_dtype : Nd4j data type. One of
        ['double', 'float', 'half']
    """
    mapping = {
        'double': np.float64,
        'float': np.float32,
        'half': np.float16
    }
    np_dtype = mapping.get(nd4j_dtype)
    if not np_dtype:
        raise Exception('Invalid nd4j data type : ' + nd4j_dtype)
    return np_dtype