How to use the plonk._units.units function in plonk

def _header_to_properties(header: dict):

    length = header['udist'] * plonk_units('cm')
    time = header['utime'] * plonk_units('s')
    mass = header['umass'] * plonk_units('g')
    magnetic_field = (
        header['umagfd']
        * plonk_units('g ** (1/2) / cm ** (1/2) / s')
        * np.sqrt(plonk_units.magnetic_constant / (4 * np.pi))
    ).to_base_units()
    units = generate_units_dictionary(length, mass, time, magnetic_field)

    prop = dict()
    prop['time'] = header['time'] * units['time']
    prop['smoothing_length_factor'] = header['hfact']

    prop['adiabatic_index'] = header['gamma']
    prop['polytropic_constant'] = 2 / 3 * header['RK2']

    ieos = header['ieos']

def str_to_units(quantity, extent, projection):
    """Convert string to plonk units.

    Parameters
    ----------
    quantity
        The units string for the quantity.
    extent
        The units string for the plot extent.
    projection
        The units string for projection interpolation.
    """
    if isinstance(quantity, str):
        quantity = plonk_units(quantity)
    elif isinstance(quantity, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine quantity unit')
    if isinstance(extent, str):
        extent = plonk_units(extent)
    elif isinstance(extent, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine extent unit')
    if isinstance(projection, str):
        projection = plonk_units(projection)
    elif isinstance(projection, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine projection unit')

----------
    quantity
        The units string for the quantity.
    extent
        The units string for the plot extent.
    projection
        The units string for projection interpolation.
    """
    if isinstance(quantity, str):
        quantity = plonk_units(quantity)
    elif isinstance(quantity, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine quantity unit')
    if isinstance(extent, str):
        extent = plonk_units(extent)
    elif isinstance(extent, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine extent unit')
    if isinstance(projection, str):
        projection = plonk_units(projection)
    elif isinstance(projection, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine projection unit')

    if extent.dimensionality != plonk_units('cm').dimensionality:
        raise ValueError('extent has incorrect dimensions')
    if projection.dimensionality != plonk_units('cm').dimensionality:
        raise ValueError('projection has incorrect dimensions')

def _header_to_properties(header: dict):

    length = header['udist'] * plonk_units('cm')
    time = header['utime'] * plonk_units('s')
    mass = header['umass'] * plonk_units('g')
    magnetic_field = (
        header['umagfd']
        * plonk_units('g ** (1/2) / cm ** (1/2) / s')
        * np.sqrt(plonk_units.magnetic_constant / (4 * np.pi))
    ).to_base_units()
    units = generate_units_dictionary(length, mass, time, magnetic_field)

    prop = dict()
    prop['time'] = header['time'] * units['time']
    prop['smoothing_length_factor'] = header['hfact']

    prop['adiabatic_index'] = header['gamma']
    prop['polytropic_constant'] = 2 / 3 * header['RK2']

    ieos = header['ieos']
    if ieos == 1:

if isinstance(extent, str):
        extent = plonk_units(extent)
    elif isinstance(extent, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine extent unit')
    if isinstance(projection, str):
        projection = plonk_units(projection)
    elif isinstance(projection, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine projection unit')

    if extent.dimensionality != plonk_units('cm').dimensionality:
        raise ValueError('extent has incorrect dimensions')
    if projection.dimensionality != plonk_units('cm').dimensionality:
        raise ValueError('projection has incorrect dimensions')

    return {'quantity': quantity, 'extent': extent, 'projection': projection}

def _header_to_properties(header: dict):

    length = header['udist'] * plonk_units('cm')
    time = header['utime'] * plonk_units('s')
    mass = header['umass'] * plonk_units('g')
    magnetic_field = (
        header['umagfd']
        * plonk_units('g ** (1/2) / cm ** (1/2) / s')
        * np.sqrt(plonk_units.magnetic_constant / (4 * np.pi))
    ).to_base_units()
    units = generate_units_dictionary(length, mass, time, magnetic_field)

    prop = dict()
    prop['time'] = header['time'] * units['time']
    prop['smoothing_length_factor'] = header['hfact']

    prop['adiabatic_index'] = header['gamma']
    prop['polytropic_constant'] = 2 / 3 * header['RK2']

The units string for projection interpolation.
    """
    if isinstance(quantity, str):
        quantity = plonk_units(quantity)
    elif isinstance(quantity, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine quantity unit')
    if isinstance(extent, str):
        extent = plonk_units(extent)
    elif isinstance(extent, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine extent unit')
    if isinstance(projection, str):
        projection = plonk_units(projection)
    elif isinstance(projection, Quantity):
        pass
    else:
        raise ValueError(f'Cannot determine projection unit')

    if extent.dimensionality != plonk_units('cm').dimensionality:
        raise ValueError('extent has incorrect dimensions')
    if projection.dimensionality != plonk_units('cm').dimensionality:
        raise ValueError('projection has incorrect dimensions')

    return {'quantity': quantity, 'extent': extent, 'projection': projection}

def set_gravitational_parameter(self, sink_idx: Union[int, List[int]]):
        """Set standard gravitational parameter.

        Calculate the standard gravitational parameter (G M) given a
        sink index, or list of sink indices for multiple systems, etc,
        and set snap.properties['gravitational_parameter']. This is
        required to calculate orbital quantities such as eccentricity
        or Stokes number.

        Parameters
        ----------
        sink_idx
            The sink index or list of indices.
        """
        G = plonk_units.newtonian_constant_of_gravitation
        if isinstance(sink_idx, (int, list)):
            M = self.sinks['mass'][sink_idx]
        else:
            raise ValueError('Cannot determine gravitational parameter')
        if self._physical_units:
            G = (G * M).to_base_units()
        else:
            G = (G * self.units['mass'] * M).to_base_units()
        self.properties['gravitational_parameter'] = G