Check if entry with same surface and energy is allready written
        to database file
        Parameters
        ----------
        chemcial_composition: str
        reaction_energy: str

        Returns id or None

def check(self, chemical_composition, reaction_energy):
        """
        Check if entry with same surface and energy is allready written
        to database file
        Parameters
        ----------
        chemcial_composition: str
        reaction_energy: str

        Returns id or None
        """
        con = self.connection or self._connect()
        self._initialize(con)
        cur = con.cursor()
        statement = """SELECT reaction.id FROM reaction WHERE
        reaction.chemical_composition=? and reaction.reaction_energy=?"""
        argument = [chemical_composition, reaction_energy]

        cur.execute(statement, argument)
        rows = cur.fetchall()
        if len(rows) > 0:
            id = rows[0][0]
        else:
            id = None
        return id