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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 descape(self, string, defs=None):
 """Decodes html entities from a given string"""

        if defs is None:
            defs = html_entities.entitydefs
        f = lambda m: defs[m.group(1)] if len(m.groups()) > 0 else m.group(0)
        return self.html_entity_re.sub(f, string)