output.put(entry.getKey(), value);
        if (entry.getValue().isEmpty()) {
          iterator.remove();
        }
      }
    }
    return output;
  }

  private boolean containsMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {
    return value != null && value.equals(get(rowKey, columnKey));
  }

        output.put(entry.getKey(), value);
        if (entry.getValue().isEmpty()) {
          iterator.remove();
        }
      }
    }
    return output;
  }

  private boolean containsMapping(
      @CheckForNull Object rowKey, @CheckForNull Object columnKey, @CheckForNull Object value) {
    return value != null && value.equals(get(rowKey, columnKey));
  }