code: def obo(self):
          
          meta = self._obo_meta()
          meta = [meta] if meta else []
          newline = "\n\n" if six.PY3 else "\n\n".encode('utf-8')
  
          try: # if 'namespace' in self.meta:
              return newline.join( meta + [
                  r.obo for r in self.typedefs
              ] + [
                  t.obo for t in self
                      if t.id.startswith(self.meta['namespace'][0])
              ])
          except KeyError:
              return newline.join( meta + [
                  r.obo for r in self.typedefs
              ] + [
                  t.obo for t in self
              ])
docs: str: the ontology serialized in obo format.