Constant CLEAR_FIELD_WHOLE 

pub const CLEAR_FIELD_WHOLE: &str = "mutation($input:ClearProjectV2ItemFieldValueInput!,$readPriority:Boolean!,$priorityName:String!,$first:Int!,$nestedFirst:Int!,$boardItems:Int!,$duplicates:Boolean!,$relationshipEvents:[IssueTimelineItemsItemType!]=[BLOCKED_BY_ADDED_EVENT,BLOCKED_BY_REMOVED_EVENT,BLOCKING_ADDED_EVENT,BLOCKING_REMOVED_EVENT,PARENT_ISSUE_ADDED_EVENT,PARENT_ISSUE_REMOVED_EVENT]){clearProjectV2ItemFieldValue(input:$input){projectV2Item{id fieldValueByName(name:$priorityName) @include(if:$readPriority){... on ProjectV2ItemFieldSingleSelectValue{name field{... on ProjectV2SingleSelectField{id name options{id name}}}}} content{__typename ...BoardIssue ... on Issue{comments(first:$first){nodes{id author{login} createdAt updatedAt body url}pageInfo{hasNextPage endCursor}}}}}}} fragment BoardIssue on Issue{__typename id number title body url createdAt updatedAt state stateReason(enableDuplicate:$duplicates) repository{nameWithOwner} parent{id} subIssuesSummary{total} commentCount:comments{totalCount} relationshipEvents:timelineItems(itemTypes:$relationshipEvents){totalCount}\n      labels(first:$nestedFirst){nodes{id name color}pageInfo{hasNextPage}}\n      projectItems(first:$boardItems){nodes{id updatedAt project{id number}\n        fieldValues(first:$nestedFirst){nodes{\n          ... on ProjectV2ItemFieldSingleSelectValue{name field{\n            ... on ProjectV2SingleSelectField{id name options{id name}}\n          }}\n          ... on ProjectV2ItemFieldTextValue{text field{... on ProjectV2Field{id name}}}\n        }pageInfo{hasNextPage}}}pageInfo{hasNextPage endCursor}}}";

CLEAR_FIELD, selecting the whole issue behind the board item cleared.