code: public boolean removeDataAttribute(DataAttribute attribute) throws LockingException {
                  if (isFieldLocked(EntryField.DATA)) {
                          if (dataUsage.containsKey(attribute)) {
                                  throw new LockingException(EntryField.DATA);
                          }
                          return false;
                  } else {
                          return dataUsage.remove(attribute) != null;
                  }
          }
docs: Removes the given attribute from the set of managed attributes.
  
  @param attribute Attribute to remove.
  @return if the set of managed attributes was modified;<br>
  <code>false</code> otherwise.
  @throws LockingException if the corresponding field is locked <br>
  and the given attribute is not already contained in the set of
  managed attributes.