code: def insert_lines(self, count=None):
          
          count = count or 1
          top, bottom = self.margins or Margins(0, self.lines - 1)
  
          # If cursor is outside scrolling margins it -- do nothin'.
          if top <= self.cursor.y <= bottom:
              self.dirty.update(range(self.cursor.y, self.lines))
              for y in range(bottom, self.cursor.y - 1, -1):
                  if y + count <= bottom and y in self.buffer:
                      self.buffer[y + count] = self.buffer[y]
                  self.buffer.pop(y, None)
  
              self.carriage_return()
docs: Insert the indicated # of lines at line with cursor. Lines
          displayed **at** and below the cursor move down. Lines moved
          past the bottom margin are lost.
  
          :param count: number of lines to insert.