code: @Nonnull
    public CSSDeclaration setExpression (@Nonnull final CSSExpression aExpression)
    {
      m_aExpression = ValueEnforcer.notNull (aExpression, "Expression");
      return this;
    }
docs: Set the expression (= value) of this declaration.
  
  @param aExpression
  The value of the property. May not be <code>null</code>.
  @return this
  @since 3.7.4