code: def list_field_append(doc, field, value):
          
          if doc.get(field) is None:
              doc[field] = []
          if not isinstance(doc[field], list):
              raise CloudantDocumentException(102, field)
          if value is not None:
              doc[field].append(value)
docs: Appends a value to a list field in a locally cached Document object.
          If a field does not exist it will be created first.
  
          :param Document doc: Locally cached Document object that can be a
              Document, DesignDocument or dict.
          :param str field: Name of the field list to append to.
          :param value: Value to append to the field list.