docs: def merge(self, other):
          """Add requirements from 'other' metadata.rb into this one."""
          if not isinstance(other, MetadataRb):
              raise TypeError("MetadataRb to merge should be a 'MetadataRb' "
                              "instance, not %s.", type(other))
          current = self.to_dict()
          new = other.to_dict()
  
          # compare and gather cookbook dependencies
          meta_writelines = ['%s\n' % self.depends_statement(cbn, meta)
                             for cbn, meta in new.get('depends', {}).items()
                             if cbn not in current.get('depends', {})]
  
          self.write_statements(meta_writelines)
          return self.to_dict()