code: protected AttributeDefinition getAttributeDefinition(final String attributeName) {
          return attributeDefinitions == null ? null : attributeDefinitions.get(attributeName);
      }
docs: Gets the {@link AttributeDefinition} provided to the constructor (if present) whose
  {@link AttributeDefinition#getName() name} matches the given {@code attributeName}.
  
  @param attributeName the attribute name
  @return the attribute definition, or {@code null} if no matching definition is found