code: public boolean isCollection(String fieldName) {
          FieldDefinition fieldDef = m_fieldDefMap.get(fieldName);
          return fieldDef != null && fieldDef.isScalarField() && fieldDef.isCollection();
      }
docs: Return true if the given field name is an MV scalar field. Since scalar fields
  must be declared as MV, only predefined fields can be MV.
  
  @param   fieldName   Candidate field name.
  @return              True if the name is a known MV scalar field, otherwise false.