This code system http://hl7.org/fhir/verificationresult-communication-method defines the following codes:

CodeDisplayDefinition
manual ManualThe information is submitted/retrieved manually (e.g. by phone, fax, paper-based)
portal PortalThe information is submitted/retrieved via a portal
pull PullThe information is retrieved (i.e. pulled) from a source (e.g. over an API)
push PushThe information is sent (i.e. pushed) from a source (e.g. over an API, asynchronously, secure messaging)
<status value="active"/><date value="2018-10-31"/><publisher value="HL7 International"/><contact><telecom><system value="other"/><value value="http://hl7.org/fhir"/></telecom></contact><description value="This code system defines the methods by which entities participating in a validation process share information (e.g. submission/retrieval of attested information, or exchange of validated information)."/><caseSensitive value="true"/><content value="complete"/><concept><code value="manual"/><display value="Manual"/><definition value="The information is submitted/retrieved manually (e.g. by phone, fax, paper-based)"/></concept><concept><code value="portal"/><display value="Portal"/><definition value="The information is submitted/retrieved via a portal"/></concept><concept><code value="pull"/><display value="Pull"/><definition value="The information is retrieved (i.e. pulled) from a source (e.g. over an API)"/></concept><concept><code value="push"/><display value="Push"/><definition value="The information is sent (i.e. pushed) from a source (e.g. over an API, asynchronously, secure messaging)"/></concept></CodeSystem>