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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 parse_all_data(self):
 """Parses the master df."""

        self._master_df.columns = ["domain", "entity", "state", "last_changed"]

        # Check if state is float and store in numericals category.
        self._master_df["numerical"] = self._master_df["state"].apply(
            lambda x: functions.isfloat(x)
        )

        # Multiindexing
        self._master_df.set_index(
            ["domain", "entity", "numerical", "last_changed"], inplace=True
        )