def pstres(self, key="", **kwargs):
    """Specifies whether prestress effects are calculated or included.

    APDL Command: PSTRES

    Parameters
    ----------
    key
        Prestress key:

        OFF - Do not calculate (or include) prestress effects (default).

        ON - Calculate (or include) prestress effects.

    Notes
    -----
    The PSTRES command specifies whether or not prestress effects are to be
    calculated or included. The command should be issued after the ANTYPE
    command.

    Prestress effects are calculated in a static or transient analysis for
    inclusion in a buckling, modal, harmonic (Method = FULL), or
    substructure generation analysis. If used in the solution processor
    (/SOLU), this command is valid only within the first load step.

    If you apply thermal body forces during a static analysis to calculate
    prestress effects, do not delete the forces during any subsequent full
    harmonic analyses. If you delete the thermal body forces, the thermal
    prestress effects will not be included in the harmonic analysis.
    Temperature loads used to define the thermal prestress will also be
    used in the full harmonic analysis as sinusoidally time-varying
    temperature loads.

    A prestress effect applied with non-follower loads resists rigid body
    rotation of the model. For example, an unsupported beam with axial
    tensile forces applied to both ends will have two nonzero rotational
    rigid body modes.

    If tabular loading (*DIM,,TABLE) was used in the prestress static
    analysis step, the corresponding value of TIME will be used for tabular
    evaluations in the modal analysis.

    This command is also valid in PREP7.
    """
    command = f"PSTRES,{key}"
    return self.run(command, **kwargs)