@Override
    public Set<byte[]> getColumnFamilyNames() {
      return Collections.unmodifiableSet(this.families.keySet());
    }
Returns all the column family names of the current table. The map of TableDescriptor contains
mapping of family name to ColumnFamilyDescriptor. This returns all the keys of the family map
which represents the column family names of the table.
@return Immutable sorted set of the keys of the families.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/TableDescriptorBuilder.java