docs: def set_principal_credit_string(self, credit_string):
          """Sets the principal credit string.
  
          arg:    credit_string (string): the new credit string
          raise:  InvalidArgument - ``credit_string`` is invalid
          raise:  NoAccess - ``Metadata.isReadOnly()`` is ``true``
          raise:  NullArgument - ``credit_string`` is ``null``
          *compliance: mandatory -- This method must be implemented.*
  
          """
          # Implemented from template for osid.repository.AssetForm.set_title_template
          self._my_map['principalCreditString'] = self._get_display_text(credit_string, self.get_principal_credit_string_metadata())