code: def free(self, block):
      # free a block returned by malloc()
      # Since free() can be called asynchronously by the GC, it could happen
      # that it's called while self._lock is held: in that case,
      # self._lock.acquire() would deadlock (issue #12352). To avoid that, a
      # trylock is used instead, and if the lock can't be acquired
      # immediately, the block is added to a list of blocks to be freed
      # synchronously sometimes later from malloc() or free(), by calling
      # _free_pending_blocks() (appending and retrieving from a list is not
      # strictly thread-safe but under CPython it's atomic thanks to the GIL).
      if os.getpid() != self._lastpid:
          raise ValueError(
              "My pid ({0:n}) is not last pid {1:n}".format(
                  os.getpid(), self._lastpid
              )
          )
      if not self._lock.acquire(False):
          # can't acquire the lock right now, add the block to the list of
          # pending blocks to free
          self._pending_free_blocks.append(block)
      else:
          # we hold the lock
          try:
              self._n_frees += 1
              self._free_pending_blocks()
              self._add_free_block(block)
              self._remove_allocated_block(block)
          finally:
              self._lock.release()
  
imports: import bisect
  from collections import defaultdict
  import mmap
  import os
  import sys
  import tempfile
  import threading
  from .context import reduction, assert_spawning
  from .None import util
label_desc: Use image node_id 10 for calling the Heap obj's underlying member method code with example usage: obj.free(block) without return types