text: import pytest
  
  
  @pytest.fixture
  def tissue_base(testapp, human_postnatal_donor_base, heart_ontology):
      item = {
          'biosample_ontology': heart_ontology['uuid'],
          'derivation_process': ['dissection'],
          'derived_from': [human_postnatal_donor_base['uuid']]
      }
      return testapp.post_json('/tissue', item, status=201).json['@graph'][0]
  
  