code: def _gen_find_command(coll, spec, projection, skip, limit, batch_size,
                        options, read_concern=DEFAULT_READ_CONCERN,
                        collation=None):
      
      cmd = SON([('find', coll)])
      if '$query' in spec:
          cmd.update([(_MODIFIERS[key], val) if key in _MODIFIERS else (key, val)
                      for key, val in spec.items()])
          if '$explain' in cmd:
              cmd.pop('$explain')
          if '$readPreference' in cmd:
              cmd.pop('$readPreference')
      else:
          cmd['filter'] = spec
  
      if projection:
          cmd['projection'] = projection
      if skip:
          cmd['skip'] = skip
      if limit:
          cmd['limit'] = abs(limit)
          if limit < 0:
              cmd['singleBatch'] = True
      if batch_size:
          cmd['batchSize'] = batch_size
      if read_concern.level:
          cmd['readConcern'] = read_concern.document
      if collation:
          cmd['collation'] = collation
  
      if options:
          cmd.update([(opt, True)
                      for opt, val in _OPTIONS.items()
                      if options & val])
      return cmd
docs: Generate a find command document.