code: def _validate_sections(cls, sections):
          
          names = []
          for section in sections:
  
              if not hasattr(section, 'name'):
                  raise ConfigurationError('`sections` attribute requires a list of Section')
  
              name = section.name
              if name in names:
                  raise ConfigurationError('`%s` section name must be unique' % name)
  
              names.append(name)
docs: Validates sections types and uniqueness.