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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 env(cls, separator=None, match=None, whitelist=None, parse_values=None, to_lower=None, convert_underscores=None):
 """Set environment variables as a source. By default all environment variables available to the process are used. This can be narrowed by the args. Args: separator: Keys are split along this character, the resulting splits are considered nested values. match: Regular expression for key matching. Keys matching the expression are considered whitelisted. whitelist: Only use environment variables that are listed in this list. parse_values: Try to parse all variable for well-known types. to_lower: Convert all variable names to lower case. convert_underscores: Convert all underscores in the name to dashes, this takes place after separation via the separator option. """

        cls.__hierarchy.append(env.Env(separator, match, whitelist, parse_values, to_lower, convert_underscores))