docs: def set_value(self, attribute, section, value):
          """
          Sets requested attribute value.
  
          Usage::
  
              >>> content = ["[Section A]\\n", "; Comment.\\n", "Attribute 1 = \\"Value A\\"\\n", "\\n", \
  "[Section B]\\n", "Attribute 2 = \\"Value B\\"\\n"]
              >>> sections_file_parser = SectionsFileParser()
              >>> sections_file_parser.content = content
              >>> sections_file_parser.parse()
              <foundations.parsers.SectionsFileParser object at 0x109304209>
              >>> sections_file_parser.set_value("Attribute 3", "Section C", "Value C")
              True
  
          :param attribute: Attribute name.
          :type attribute: unicode
          :param section: Section containing the searched attribute.
          :type section: unicode
          :param value: Attribute value.
          :type value: object
          :return: Definition success.
          :rtype: bool
          """
  
          if not self.section_exists(section):
              LOGGER.debug("> Adding '{0}' section.".format(section))
              self.__sections[section] = OrderedDict() if self.__preserve_order else dict()
  
          self.__sections[section][attribute] = value
  
          return True