'Parse timestamp expression
@param timestamp: the timestamp expression'

@staticmethod
def parse_timestamp(timestamp):

    if timestamp:
        fields = timestamp.split(',')
        if (len(fields) > 1):
            start = fields[0].strip()
            end = fields[1].strip()
        else:
            start = fields[0].strip()
            end = None
    else:
        start = None
        end = None
    return (start, end)
