code: def write_relationships(self, file_name, flat=True):
          
          with open(file_name, 'w') as writer:
              if flat:
                  self._write_relationships_flat(writer)
              else:
                  self._write_relationships_non_flat(writer)
docs: This module will output the eDNA tags which are used inside each
          calculation.
  
          If flat=True, data will be written flat, like:
              ADE1CA01, ADE1PI01, ADE1PI02
  
          If flat=False, data will be written in the non-flat way, like:
              ADE1CA01, ADE1PI01
              ADE1CA01, ADE1PI02
  
          :param file_name: the output filename to write the relationships,
                            which should include the '.csv' extension
          :param flat: True or False