def calculate_P(self, T, P, method):
if method == COOLPROP:<EOL><INDENT>mu = PropsSI('<STR_LIT>', '<STR_LIT:T>', T, '<STR_LIT:P>', P, self.CASRN)<EOL><DEDENT>elif method in self.tabular_data:<EOL><INDENT>mu = self.interpolate_P(T, P, method)<EOL><DEDENT>return mu<EOL>
r'''Method to calculate pressure-dependent gas viscosity
        at temperature `T` and pressure `P` with a given method.

        This method has no exception handling; see `TP_dependent_property`
        for that.

        Parameters
        ----------
        T : float
            Temperature at which to calculate gas viscosity, [K]
        P : float
            Pressure at which to calculate gas viscosity, [K]
        method : str
            Name of the method to use

        Returns
        -------
        mu : float
            Viscosity of the gas at T and P, [Pa*]