code: def is_empty(self):
          
          ps = self.p_lst
          if len(ps) > 1:
              return False
  
          if not ps:
              raise InvalidXmlError('p:txBody must have at least one a:p')
  
          if ps[0].text != '':
              return False
          return True
docs: True if only a single empty `a:p` element is present.