code: def is_all_Ns(self, start=0, end=None):
          '''Returns true if the sequence is all Ns (upper or lower case)'''
          if end is not None:
              if start > end:
                  raise Error('Error in is_all_Ns. Start coord must be <= end coord')
              end += 1
          else:
              end = len(self)
  
          if len(self) == 0:
              return False
          else:
              return re.search('[^Nn]', self.seq[start:end]) is Nonf is_all_Ns(self, start=0, end=None):
          '''Returns true if the sequence is all Ns (upper or lower case)'''
          if end is not None:
              if start > end:
                  raise Error('Error in is_all_Ns. Start coord must be <= end coord')
              end += 1
          else:
              end = len(self)
  
          if len(self) == 0:
              return False
          else:
              return re.search('[^Nn]', self.seq[start:end]) is None
docs: Returns true if the sequence is all Ns (upper or lower case)