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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_section(self, section_name):
 """Create a section of the report, to be headed by section_name Text and images can be added by using the `section` argument of the `add_text` and `add_image` methods. Sections can also be ordered by using the `set_section_order` method. By default, text and images that have no section will be placed after all the sections, in the order they were added. This behavior may be altered using the `sections_first` attribute of the `make_report` method. """

        self.section_headings.append(section_name)
        if section_name in self.sections:
            raise ValueError("Section %s already exists." % section_name)
        self.sections[section_name] = []
        return