Writes the header to file.

def write_case_data(self, file):
        """ Writes the header to file.
        """
#        title = "Power Flow Solution"
#        file.write("=" * len(title))
#        file.write("\n")
#        file.write("\n%s\n" % title)
#        file.write("=" * len(title))
#        file.write("\n")

        # Document subtitle.
        subtitle = self.case.name
        file.write("-" * len(subtitle))
        file.write("\n%s\n" % subtitle)
        file.write("-" * len(subtitle))
        file.write("\n")

        file.write("System Summary\n")
        file.write("-" * 14)
        file.write("\n")

        self.write_how_many(file)
        self.write_how_much(file)
        self.write_min_max(file)