code: def _copy_to(self, curs, srec):
      f = StringIO()
      curs.copy_to(MinimalWrite(f), "tcopy")
  
      f.seek(0)
      ntests = 0
      for line in f:
          n, s = line.split()
          if int(n) < len(string.ascii_letters):
              self.assertEqual(s, string.ascii_letters[int(n)] * srec)
              ntests += 1
  
      self.assertEqual(ntests, len(string.ascii_letters))
  
imports: import io
  import sys
  import string
  import unittest
  from .testutils import ConnectingTestCase, skip_before_postgres, slow, StringIO
  from .testutils import skip_if_crdb
  from itertools import cycle
  from subprocess import Popen, PIPE
  import psycopg2
  import psycopg2.extensions
  from .testutils import skip_copy_if_green, TextIOBase
  from .testconfig import dsn
label_desc: Use image node_id 12 for calling the CopyTests obj's underlying member method code with example usage: obj._copy_to(curs, srec) without return types