<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def start_tag(self, name, attrs=None):
 """Open an XML tag"""

        if not attrs:
            self._write('<%s>' % name)
        else:
            self._write('<' + name)
            for (name, value) in sorted(attrs.items()):
                self._write(
                    ' %s=%s' % (name, quoteattr(scientificformat(value))))
            self._write('>')
        self.indentlevel += 1