code: def make_coalesced_expr(
      table_aliases: Sequence[str], column_alias: str
  ) -> SqlExpressionNode:
      """Makes a coalesced expression of the given column from the given table aliases.
  
      e.g.
  
      table_aliases = ["a", "b"]
      column_alias = "is_instant"
  
      ->
  
      COALESCE(a.is_instant, b.is_instant)
      """
      if len(table_aliases) == 1:
          return SqlColumnReferenceExpression(
              col_ref=SqlColumnReference(
                  table_alias=table_aliases[0],
                  column_name=column_alias,
              )
          )
      else:
          columns_to_coalesce: List[SqlExpressionNode] = []
          for table_alias in table_aliases:
              columns_to_coalesce.append(
                  SqlColumnReferenceExpression(
                      col_ref=SqlColumnReference(
                          table_alias=table_alias,
                          column_name=column_alias,
                      )
                  )
              )
          return SqlAggregateFunctionExpression(
              sql_function=SqlFunction.COALESCE,
              sql_function_args=columns_to_coalesce,
          )
  
imports: from __future__ import annotations
  from typing import List, Sequence
  from metricflow.sql.sql_exprs import SqlAggregateFunctionExpression, SqlColumnReference, SqlColumnReferenceExpression, SqlExpressionNode, SqlFunction
label_desc: Use image node_id 1 for calling a global function with example usage: make_coalesced_expr(table_aliases, column_alias) and returns: SqlColumnReferenceExpression, SqlAggregateFunctionExpression