code: def validate(self):
          
          self.normalize()
  
          if self._node is None:
              logging.debug('The node is empty, and cannot be validated.')
              return False
  
          if self._schema is None:
              self._schema = XMLSchema(self._schemadoc)
  
          is_valid = self._schema.validate(self._node)
  
          for msg in self._schema.error_log:
              logging.info('Line:%d, Column:%d -- %s', msg.line, msg.column, msg.message)
  
          return is_valid
docs: Validate the current file against the SLD schema. This first normalizes
          the SLD document, then validates it. Any schema validation error messages
          are logged at the INFO level.
  
          @rtype: boolean
          @return: A flag indicating if the SLD is valid.