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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _LeaseFlowProcessingReqests(self, cursor=None):
 """Leases a number of flow processing requests."""

    now = rdfvalue.RDFDatetime.Now()
    expiry = now + rdfvalue.Duration("10m")

    query = """
      UPDATE flow_processing_requests
      SET leased_until=FROM_UNIXTIME(%(expiry)s), leased_by=%(id)s
      WHERE
       (delivery_time IS NULL OR
        delivery_time <= NOW(6)) AND
       (leased_until IS NULL OR
        leased_until < NOW(6))
      LIMIT %(limit)s
    """

    id_str = utils.ProcessIdString()
    args = {
        "expiry": mysql_utils.RDFDatetimeToTimestamp(expiry),
        "id": id_str,
        "limit": 50,
    }

    updated = cursor.execute(query, args)

    if updated == 0:
      return []

    query = """
      SELECT UNIX_TIMESTAMP(timestamp), request
      FROM flow_processing_requests
      FORCE INDEX (flow_processing_requests_by_lease)
      WHERE leased_by=%(id)s AND leased_until=FROM_UNIXTIME(%(expiry)s)
      LIMIT %(updated)s
    """

    args = {
        "expiry": mysql_utils.RDFDatetimeToTimestamp(expiry),
        "id": id_str,
        "updated": updated,
    }

    cursor.execute(query, args)

    res = []
    for timestamp, request in cursor.fetchall():
      req = rdf_flows.FlowProcessingRequest.FromSerializedString(request)
      req.timestamp = mysql_utils.TimestampToRDFDatetime(timestamp)
      req.leased_until = expiry
      req.leased_by = id_str
      res.append(req)

    return res