code: def validate(self):
          
          if not self.id or len(self.id) == 0:
              raise ValidationError('No <id> tag')
          if not self.name or len(self.name) == 0:
              raise ValidationError('No <name> tag')
          if not self.summary or len(self.summary) == 0:
              raise ValidationError('No <summary> tag')
          if not self.description or len(self.description) == 0:
              raise ValidationError('No <description> tag')
          if self.kind == 'firmware':
              if len(self.provides) == 0:
                  raise ValidationError('No <provides> tag')
              if len(self.releases) == 0:
                  raise ValidationError('No <release> tag')
          if self.kind == 'desktop':
              if len(self.screenshots) == 0:
                  raise ValidationError('No <screenshot> tag')
          if not self.metadata_license or len(self.metadata_license) == 0:
              raise ValidationError('No <metadata_license> tag')
          valid_licenses = [
              'CC0-1.0',
              'CC-BY-3.0',
              'CC-BY-4.0',
              'CC-BY-SA-3.0',
              'CC-BY-SA-4.0',
              'GFDL-1.1',
              'GFDL-1.2',
              'GFDL-1.3',
              'FSFAP'
          ]
          if self.metadata_license not in valid_licenses:
              raise ValidationError('Invalid <metadata_license> tag')
          if not self.project_license or len(self.project_license) == 0:
              raise ValidationError('No <project_license> tag')
          if not self.developer_name or len(self.developer_name) == 0:
              raise ValidationError('No <developer_name> tag')
  
          # verify release objects
          for rel in self.releases:
              if not rel.version or len(rel.version) == 0:
                  raise ValidationError('No version in <release> tag')
              if rel.timestamp == 0:
                  raise ValidationError('No timestamp in <release> tag')
docs: Parse XML data