dot sign does not work in grid-template-areas code example

Example 1: grid-template-areas css

#page {
  display: grid;
  width: 100%;
  height: 250px;
  grid-template-areas: "head head"
                       "nav  main"
                       "nav  foot";
  grid-template-rows: 50px 1fr 30px;
  grid-template-columns: 150px 1fr;
}

#page > header {
  grid-area: head;
  background-color: #8ca0ff;
}

#page > nav {
  grid-area: nav;
  background-color: #ffa08c;
}

#page > main {
  grid-area: main;
  background-color: #ffff64;
}

#page > footer {
  grid-area: foot;
  background-color: #8cffa0;
}

Example 2: unknown property grid-template-areas

.sidebar{
    	grid-area:sidebar;
      background:aqua;

    }
    .grid_container{
    	display:grid;
    	grid-template-columns: 1fr 3fr;
      grid-template-rows: 1fr 3fr;
    	grid-template-areas:
    	"sidebar ."
    	"sidebar .";
      background:pink;
      height:300px;
    }