code: def initialise(self):
          
          self._checkWriteMode()
          self._createSystemTable()
          self._createNetworkTables()
          self._createOntologyTable()
          self._createReferenceSetTable()
          self._createReferenceTable()
          self._createDatasetTable()
          self._createReadGroupSetTable()
          self._createReadGroupTable()
          self._createCallSetTable()
          self._createVariantSetTable()
          self._createVariantAnnotationSetTable()
          self._createFeatureSetTable()
          self._createContinuousSetTable()
          self._createBiosampleTable()
          self._createIndividualTable()
          self._createPhenotypeAssociationSetTable()
          self._createRnaQuantificationSetTable()
docs: Initialise this data repository, creating any necessary directories
          and file paths.