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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 expect_file_to_exist(self, filepath=None, result_format=None, include_config=False, catch_exceptions=None, meta=None):
 """ Checks to see if a file specified by the user actually exists Args: filepath (str or None):
 \ The filepath to evalutate. If none, will check the currently-configured path object of this FileDataAsset. Keyword Args: result_format (str or None):
 \ Which output mode to use: `BOOLEAN_ONLY`, `BASIC`, `COMPLETE`, or `SUMMARY`. For more detail, see :ref:`result_format <result_format>`. include_config (boolean):
 \ If True, then include the expectation config as part of the result object. \ For more detail, see :ref:`include_config`. catch_exceptions (boolean or None):
 \ If True, then catch exceptions and include them as part of the result object. \ For more detail, see :ref:`catch_exceptions`. meta (dict or None):
 \ A JSON-serializable dictionary (nesting allowed) that will be included in the output without modification. For more detail, see :ref:`meta`. Returns: A JSON-serializable expectation result object. Exact fields vary depending on the values passed to :ref:`result_format <result_format>` and :ref:`include_config`, :ref:`catch_exceptions`, and :ref:`meta`. """


        if filepath is not None and os.path.isfile(filepath):
            success = True
        elif self._path is not None and os.path.isfile(self._path):
            success = True
        else:
            success = False

        return {"success":success}