code: @CheckReturnValue
      public MessageAction appendFormat(final String format, final Object... args)
      {
          return append(String.format(format, args));
      }
docs: Applies the result of {@link String#format(String, Object...) String.format(String, Object...)}
  as content.
  
  <p>For more information of formatting review the {@link java.util.Formatter Formatter} documentation!
  
  @param  format
  The format String
  @param  args
  The arguments that should be used for conversion
  
  @throws java.lang.IllegalArgumentException
  If the appended formatting is too big and will cause the content to
  exceed the {@value net.dv8tion.jda.core.entities.Message#MAX_CONTENT_LENGTH} character limit
  @throws java.util.IllegalFormatException
  If a format string contains an illegal syntax,
  a format specifier that is incompatible with the given arguments,
  insufficient arguments given the format string, or other illegal conditions.
  For specification of all possible formatting errors,
  see the <a href="../util/Formatter.html#detail">Details</a>
  section of the formatter class specification.
  
  @return Updated MessageAction for chaining convenience