code: public Filters withChannels(String... channels) {
          if (this.channels == null) {
              setChannels(new java.util.ArrayList<String>(channels.length));
          }
          for (String ele : channels) {
              this.channels.add(ele);
          }
          return this;
      }
docs: <p>
  The Channel to use as a filter for the metrics returned. Only VOICE is supported.
  </p>
  <p>
  <b>NOTE:</b> This method appends the values to the existing list (if any). Use
  {@link #setChannels(java.util.Collection)} or {@link #withChannels(java.util.Collection)} if you want to override
  the existing values.
  </p>
  
  @param channels
  The Channel to use as a filter for the metrics returned. Only VOICE is supported.
  @return Returns a reference to this object so that method calls can be chained together.
  @see Channel