public boolean __getInMemory() {
    Object o = attrs.get(IN_MEMORY);
    return o != null
      ? Boolean.parseBoolean(o.toString())
      : ColumnFamilyDescriptorBuilder.DEFAULT_IN_MEMORY;
  }
Returns true if the IN_MEMORY attribute is present and true
hbase-rest/src/main/java/org/apache/hadoop/hbase/rest/model/ColumnSchemaModel.java