code: def to_gremlin(self):
          
          self.validate()
  
          template = (
              u'transform{{'
              u'it, m -> new com.orientechnologies.orient.core.record.impl.ODocument([ {} ])'
              u'}}')
  
          field_representations = (
              u'{name}: {expr}'.format(name=key, expr=self.fields[key].to_gremlin())
              for key in sorted(self.fields.keys())  # Sort the keys for deterministic output order.
          )
          return template.format(u', '.join(field_representations))
docs: Return a unicode object with the Gremlin representation of this block.