code: def get_cancer_types(cancer_filter=None):
      
      data = {'cmd': 'getTypesOfCancer'}
      df = send_request(**data)
      res = _filter_data_frame(df, ['type_of_cancer_id'], 'name', cancer_filter)
      type_ids = list(res['type_of_cancer_id'].values())
      return type_ids
docs: Return a list of cancer types, optionally filtered.
  
      Parameters
      ----------
      cancer_filter : Optional[str]
          A string used to filter cancer types. Its value is the name or
          part of the name of a type of cancer. Example: "melanoma",
          "pancreatic", "non-small cell lung"
  
      Returns
      -------
      type_ids : list[str]
          A list of cancer types matching the filter.
          Example: for cancer_filter="pancreatic", the result includes
          "panet" (neuro-endocrine) and "paad" (adenocarcinoma)