def is_nullable(column_elt):
    """
    Identify whether a column is nullable.
    @param IN column_elt Column XML element
    @return True if it's nullable, False otherwise
    """

    col_nullable = column_elt.get("nullable")
    if not col_nullable:
        raise Exception("Missing column 'nullable' attribute")
    return col_nullable.lower() == "true"