code: def get_DID_subdomain(did, db_path=None, zonefiles_dir=None, atlasdb_path=None, check_pending=False):
      
      opts = get_blockstack_opts()
      if not is_subdomains_enabled(opts):
          log.warn("Subdomain support is disabled")
          return None
  
      if db_path is None:
          db_path = opts['subdomaindb_path']
  
      if zonefiles_dir is None:
          zonefiles_dir = opts['zonefiles']
      
      if atlasdb_path is None:
          atlasdb_path = opts['atlasdb_path']
  
      db = SubdomainDB(db_path, zonefiles_dir)
      try:
          subrec = db.get_DID_subdomain(did)
      except Exception as e:
          if BLOCKSTACK_DEBUG:
              log.exception(e)
  
          log.warn("Failed to load subdomain for {}".format(did))
          return None
  
      if check_pending:
          # make sure that all of the zone files between this subdomain's
          # domain's creation and this subdomain's zone file index are present,
          # minus the ones that are allowed to be missing.
          subrec.pending = db.subdomain_check_pending(subrec, atlasdb_path)
  
      return subrec
docs: Static method for resolving a DID to a subdomain
      Return the subdomain record on success
      Return None on error