Helper method to get a list of ComputedEntries in a chemical system.
        For example, elements = ["Li", "Fe", "O"] will return a list of all
        entries in the Li-Fe-O chemical system, i.e., all LixOy,
        FexOy, LixFey, LixFeyOz, Li, Fe and O phases. Extremely useful for
        creating phase diagrams of entire chemical systems.

        Args:
            elements ([str]): List of element symbols, e.g., ["Li", "Fe",
                "O"].
            compatible_only (bool): Whether to return only "compatible"
                entries. Compatible entries are entries that have been
                processed using the MaterialsProjectCompatibility class,
                which performs adjustments to allow mixing of GGA and GGA+U
                calculations for more accurate phase diagrams and reaction
                energies.
            inc_structure (str): If None, entries returned are
                ComputedEntries. If inc_structure="final",
                ComputedStructureEntries with final structures are returned.
                Otherwise, ComputedStructureEntries with initial structures
                are returned.
            property_data (list): Specify additional properties to include in
                entry.data. If None, no data. Should be a subset of
                supported_properties.
            conventional_unit_cell (bool): Whether to get the standard
                conventional unit cell

        Returns:
            List of ComputedEntries.

def get_entries_in_chemsys(self, elements, compatible_only=True,
                               inc_structure=None, property_data=None,
                               conventional_unit_cell=False):
        """
        Helper method to get a list of ComputedEntries in a chemical system.
        For example, elements = ["Li", "Fe", "O"] will return a list of all
        entries in the Li-Fe-O chemical system, i.e., all LixOy,
        FexOy, LixFey, LixFeyOz, Li, Fe and O phases. Extremely useful for
        creating phase diagrams of entire chemical systems.

        Args:
            elements ([str]): List of element symbols, e.g., ["Li", "Fe",
                "O"].
            compatible_only (bool): Whether to return only "compatible"
                entries. Compatible entries are entries that have been
                processed using the MaterialsProjectCompatibility class,
                which performs adjustments to allow mixing of GGA and GGA+U
                calculations for more accurate phase diagrams and reaction
                energies.
            inc_structure (str): If None, entries returned are
                ComputedEntries. If inc_structure="final",
                ComputedStructureEntries with final structures are returned.
                Otherwise, ComputedStructureEntries with initial structures
                are returned.
            property_data (list): Specify additional properties to include in
                entry.data. If None, no data. Should be a subset of
                supported_properties.
            conventional_unit_cell (bool): Whether to get the standard
                conventional unit cell

        Returns:
            List of ComputedEntries.
        """
        entries = []
        for i in range(len(elements)):
            for els in itertools.combinations(elements, i + 1):
                entries.extend(
                    self.get_entries(
                        "-".join(els), compatible_only=compatible_only,
                        inc_structure=inc_structure,
                        property_data=property_data,
                        conventional_unit_cell=conventional_unit_cell))
        return entries