code: @Nonnull
      public BugInstance addField(String className, String fieldName, String fieldSig, boolean isStatic) {
          addField(new FieldAnnotation(className, fieldName, fieldSig, isStatic));
          return this;
      }
docs: Add a field annotation.
  
  @param className
  name of the class containing the field
  @param fieldName
  the name of the field
  @param fieldSig
  type signature of the field
  @param isStatic
  whether or not the field is static
  @return this object