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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 srcnode(self):
 """If this node is in a build path, return the node corresponding to its source file. Otherwise, return ourself. """

        srcdir_list = self.dir.srcdir_list()
        if srcdir_list:
            srcnode = srcdir_list[0].Entry(self.name)
            srcnode.must_be_same(self.__class__)
            return srcnode
        return self