code: def begin(self, sql=None):
          
          self._transaction = True
          try:
              begin = self._con.begin
          except AttributeError:
              return self._con.query(sql or 'begin')
          else:
              # use existing method if available
              if sql:
                  return begin(sql=sql)
              else:
                  return begin()
docs: Begin a transaction.