code: func (p *Projection) GetColumn(tableName, columnName string) (*types.SQLTableColumn, error) {
  	if table, ok := p.Tables[tableName]; ok {
  		column := table.GetColumn(columnName)
  		if column == nil {
  			return nil, fmt.Errorf("GetColumn: table '%s' has no column '%s'",
  				tableName, columnName)
  		}
  		return column, nil
  	}
  
  	return nil, fmt.Errorf("GetColumn: table does not exist projection: %s ", tableName)
  }
docs: // Get the column for a particular table and column name