def append(values)
      coa!
      if values.is_a?(VarSet)
        values.send(:coa!)
        @coa_vars = values.instance_variable_get(:@coa_vars) + @coa_vars
      else
        @my_vars = deep_dup(values)
      end
      self
    end
def append(values)
      coa!
      if values.is_a?(VarSet)
        values.send(:coa!)
        @coa_vars = values.instance_variable_get(:@coa_vars) + @coa_vars
      else
        @my_vars = deep_dup(values)
      end
      self
    end
Add or overwrite a set of variables.

 @param values [VarSet, Hash] New set of variables.

 @return [VarSet] Returns self.