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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 request(self, source="candidate"):
 """Validate the contents of the specified configuration. *source* is the name of the configuration datastore being validated or `config` element containing the configuration subtree to be validated :seealso: :ref:`srctarget_params`"""

        node = new_ele("validate")
        if type(source) is str:
            src = util.datastore_or_url("source", source, self._assert)
        else:
            validated_element(source, ("config", qualify("config")))
            src = new_ele("source")
            src.append(source)
        node.append(src)
        return self._request(node)