def create_migration_method_hashes
      # the class => attribute => migration filter hash
      @attr_flt_hash = {}
      customizable_class_attributes.each do |klass, pas|
        flts = migration_filters(klass) || next
        @attr_flt_hash[klass] = flts
      end
      # print the migration shim methods
      unless @mgt_mths.empty? then
        logger.info("Migration shim methods:\n#{@mgt_mths.qp}")
      end
    end
def create_migration_method_hashes
      # the class => attribute => migration filter hash
      @attr_flt_hash = {}
      customizable_class_attributes.each do |klass, pas|
        flts = migration_filters(klass) || next
        @attr_flt_hash[klass] = flts
      end
      # print the migration shim methods
      unless @mgt_mths.empty? then
        logger.info("Migration shim methods:\n#{@mgt_mths.qp}")
      end
    end
Creates the class => +migrate_+_<attribute>_ hash for the given klasses.