Match variable names to docs

Update variable name style (and comments) to match docs

src/machines.jl

@@ -580,10 +580,10 @@ or none of the following apply:
    changed since the last time `mach` was trained (ie, the last time
    `mach.state` was last incremented).
 
-4.  The specified `rows` have changed since the last retraining and
+4. The specified `rows` have changed since the last retraining and
    `mach.model` does not have `Static` type.
 
-5.  `mach.model` is a model and different from the last model used for training, but has
+5. `mach.model` is a model and different from the last model used for training, but has
    the same type.
 
 6. `mach.model` is a model but has a type different from the last model used for
@@ -658,7 +658,7 @@ function fit_only!(
     rows === nothing && (rows = (:))
     rows_is_new = !isdefined(mach, :old_rows) || rows != mach.old_rows
 
-    condition_iv = rows_is_new && !(mach.model isa Static)
+    condition_4 = rows_is_new && !(mach.model isa Static)
 
     upstream_has_changed = mach.old_upstream_state != upstream_state
 
@@ -672,16 +672,16 @@ function fit_only!(
 
     # build or update cached `resampled_data` if necessary (`mach.data` is already defined
     # above if needed here):
-    if cache_data && (!data_is_valid || condition_iv)
+    if cache_data && (!data_is_valid || condition_4)
         mach.resampled_data = selectrows(model, rows, mach.data...)
     end
 
     # `fit`, `update`, or return untouched:
-    if mach.state == 0 ||       # condition (i)
-        force == true ||        # condition (ii)
-        upstream_has_changed || # condition (iii)
-        condition_iv ||         # condition (iv)
-        modeltype_changed       # conditions (vi) or (vii)
+    if mach.state == 0 ||       # condition (1)
+        force == true ||        # condition (2)
+        upstream_has_changed || # condition (3)
+        condition_4 ||          # condition (4)
+        modeltype_changed       # conditions (6) or (7)
 
         isdefined(mach, :report) || (mach.report = LittleDict{Symbol,Any}())
 
@@ -709,7 +709,7 @@ function fit_only!(
                 rethrow()
             end
 
-    elseif model != mach.old_model # condition (v)
+    elseif model != mach.old_model # condition (5)
 
         # update the model:
         fitlog(mach, :update, verbosity)