code: def push(self, lines):
      self.lines = list(lines)[::-1]
  
imports: import unittest
  import io
  from idlelib.PyShell import PseudoInputFile, PseudoOutputFile
  from test import test_support
label_desc: Use image node_id 6 for calling the MockShell obj's underlying member method code with example usage: obj.push(lines) without return types