code: private RequestBody createBody() {
  		RequestBody rqBody = null;
  
  		// Try request body first.
  		if (body != null && !body.isEmpty()) {
  			rqBody = RequestBody.create(null, body);
  		}
  		else if (!formParams.isEmpty()) {
  			FormBody.Builder builder = new FormBody.Builder();
  			for (HttpParameter parameter : formParams.values()) {
  				String encodedName = parameter.getEncodedName();
  				String encodedValue = firstNonNull(parameter.getEncodedValue(), "");
  				builder.addEncoded(encodedName, encodedValue);
  			}
  
  			rqBody = builder.build();
  		}
  
  		return rqBody;
  	}
docs: Create the OkHttp request body:
  <ul>
  <li>Create body from {@link #body} value if it is defined.</li>
  <li>Create {@link FormBody} from {@link #formParams} otherwise if it is not empty.</li>
  <li>Returns {@code null} otherwise.</li>
  </ul>
  
  @return OkHttp {@link RequestBody} instance.
  @see RequestBody#create(MediaType, String)
  @see FormBody