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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 _to_snake_case(string):
 """Return a snake cased version of the input string. Args: string (str):
 A camel cased string. Returns: str: A snake cased string. """

        sub_string = r'\1_\2'
        string = REGEX_CAMEL_FIRST.sub(sub_string, string)
        return REGEX_CAMEL_SECOND.sub(sub_string, string).lower()