code: def try_get_column(column_name, node, context):
      
      selectable = get_node_selectable(node, context)
      if not hasattr(selectable, 'c'):
          raise AssertionError(
              u'Selectable "{}" does not have a column collection. Context is {}.'.format(
                  selectable, context))
      return selectable.c.get(column_name, None)
docs: Attempt to get a column by name from the selectable.
  
      Args:
          column_name: str, name of the column to retrieve.
          node: SqlNode, the node the column is being retrieved for.
          context: CompilationContext, compilation specific metadata.
  
      Returns:
          Optional[column], the SQLAlchemy column if found, None otherwise.