'Parse a string expression and convert it into a dict
of filters (S3ResourceQueries).
@parameter expression: the filter expression as string
@return: a dict of {component_alias: filter_query}'

def parse(self, expression):

    query = {}
    parser = self.parser
    if ((not expression) or (parser is None)):
        return query
    try:
        parsed = parser.parseString(expression)
    except self.ParseException:
        current.log.error(("Invalid    URL    Filter    Expression:    '%s'" % expression))
    else:
        if parsed:
            query = self.convert_expression(parsed[0])
    return query
