code: def get_one_meth_category(self, category, all_codes, code_types):
          
          categories = Series(code_types[code_types[category] == True].index)
          cond = all_codes['dtype'].isin(categories)
          codes = all_codes[cond]
          return codes
docs: Get all codes in one category (i.e., all pmag codes).
          This can include multiple method types (i.e., 'anisotropy_estimation', 'sample_prepartion', etc.)