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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 _collapse_default(self, entry):
 """Collapses the list structure in entry to a single string representing the default value assigned to a variable or its dimensions. """

        if isinstance(entry, tuple) or isinstance(entry, list):
            sets = []
            i = 0
            while i < len(entry):
                if isinstance(entry[i], str) and i+1 < len(entry) and isinstance(entry[i+1], list):
                    sets.append((entry[i], entry[i+1]))
                    i += 2
                elif isinstance(entry[i], str) and entry[i] == ",":
                    i += 1
                else:
                    sets.append((entry[i],))
                    i += 1

            result = []
            for s in sets:
                if isinstance(s[0], str):
                    name = s[0].strip(",")
                elif len(s) == 1:
                    name = self._collapse_default(s[0])
                    
                if len(s) > 1:
                    args = self._collapse_default(s[1])
                else:
                    args = []
                if len(args) > 0:
                    result.append("{}({})".format(name, args))
                else:
                    result.append(name)

            return ', '.join(result)
        else:
            if "," in entry:
                return entry.split(",")[0].strip()
            else:
                return entry.strip()