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| <?xml version="1.0" encoding="windows-1252"?> |
| <!-- DFIN - Donnelley Financial Solutions, Inc. --> |
| <!-- CTU Version: 72.2.5 --> |
| <!-- Creation date: 3/29/2024 8:55:17 AM Eastern Time --> |
| <!-- Copyright (c) 2024 Donnelley Financial Solutions, Inc. All Rights Reserved. --> |
| <xsd:schema xmlns:ato="http://dfinsolutions.com/20240328" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2022-03-31" xmlns:dei="http://xbrl.sec.gov/dei/2023" xmlns:stpr="http://xbrl.sec.gov/stpr/2023" xmlns:us-types="http://fasb.org/us-types/2023" xmlns:srt="http://fasb.org/srt/2023" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://dfinsolutions.com/20240328" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> |
| <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/instance"/> |
| <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/linkbase"/> |
| <xsd:import schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" namespace="http://xbrl.org/2005/xbrldt"/> |
| <xsd:import schemaLocation="https://www.xbrl.org/dtr/type/2022-03-31/types.xsd" namespace="http://www.xbrl.org/dtr/type/2022-03-31"/> |
| <xsd:import schemaLocation="https://xbrl.sec.gov/dei/2023/dei-2023.xsd" namespace="http://xbrl.sec.gov/dei/2023"/> |
| <xsd:import schemaLocation="https://xbrl.sec.gov/stpr/2023/stpr-2023.xsd" namespace="http://xbrl.sec.gov/stpr/2023"/> |
| <xsd:import schemaLocation="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd" namespace="http://fasb.org/srt/2023"/> |
| <xsd:annotation> |
| | <xsd:appinfo> |
| | | <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ato-20240328_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:title="Label Links, all" xlink:type="simple"/> |
| | | <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ato-20240328_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:title="Presentation Links, all" xlink:type="simple"/> |
| | | <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="ato-20240328_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:title="Definition Links, all" xlink:type="simple"/> |
| | | <link:roleType roleURI="http://dfinsolutions.com//20240328/taxonomy/role/DocumentDocumentAndEntityInformation" id="DocumentDocumentAndEntityInformation"> |
| <link:definition> 000001 - Document - Document and Entity Information </link:definition> |
| <link:usedOn> link:calculationLink </link:usedOn> |
| <link:usedOn> link:presentationLink </link:usedOn> |
| <link:usedOn> link:definitionLink </link:usedOn> |
| </link:roleType> |
| | | </xsd:appinfo> |
| | </xsd:annotation> |
| <xsd:element id="ato_DocumentAndEntityInformationTable" name="DocumentAndEntityInformationTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/> |
| <xsd:element id="ato_DocumentAndEntityInformationLineItems" name="DocumentAndEntityInformationLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/> |
| </xsd:schema> |
