code: def validate(self, require_all=True, scale='colors'):
          
          super(self.__class__, self).validate()
          required_attribs = ('data', 'scales', 'axes', 'marks')
          for elem in required_attribs:
              attr = getattr(self, elem)
              if attr:
                  # Validate each element of the sets of data, etc
                  for entry in attr:
                      entry.validate()
                  names = [a.name for a in attr]
                  if len(names) != len(set(names)):
                      raise ValidationError(elem + ' has duplicate names')
              elif require_all:
                  raise ValidationError(
                      elem + ' must be defined for valid visualization')
docs: Validate the visualization contents.
  
          Parameters
          ----------
          require_all : boolean, default True
              If True (default), then all fields ``data``, ``scales``,
              ``axes``, and ``marks`` must be defined. The user is allowed to
              disable this if the intent is to define the elements
              client-side.
  
          If the contents of the visualization are not valid Vega, then a
          :class:`ValidationError` is raised.