docs: def context(self):
          """Build the interpolation context from the schemas"""
  
          # Can't use self.columns b/c of recursion with resolved_url
  
          t = self.schema_term
  
          if not t:
              return {}
  
          sql_columns = []
          all_columns = []
  
          for i, c in enumerate(t.children):
              if c.term_is("Table.Column"):
                  p = c.all_props
  
                  if p.get('sqlselect'): # has a value for SqlSqlect
                      sql_columns.append(p.get('sqlselect'))
  
                  all_columns.append(c.name)
  
          return {
              'SQL_COLUMNS': ', '.join(sql_columns),
              'ALL_COLUMNS': ', '.join(all_columns)
          }