expression {
  call_expr {
    function: "_==_"
    args {
      call_expr {
        function: "_[_]"
        args {
          select_expr {
            operand {
              select_expr {
                operand {
                  ident_expr {
                    name: "xds"
                  }
                }
                field: "upstream_host_metadata"
              }
            }
            field: "filter_metadata"
          }
          const_expr {
            string_value: "other"
          }
              }
        const_expr {
          string_value: "label"
        }
      }
      const_expr {
        string_value: "prod"
      }
    }
  }
}
stream_info {
  start_time: 1522796769123
  upstream_metadata {
    filter_metadata {
      key: "other"
      value: {
        fields {
          key: "label"
          value: { string_value: "prod" }
        }
      }
    }
  }
}
