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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 describe_token_expr(expr):
 """Like `describe_token` but for token expressions."""

    if ':' in expr:
        type, value = expr.split(':', 1)
        if type == 'name':
            return value
    else:
        type = expr
    return _describe_token_type(type)