code: def test_nested_function_expr(
      default_expr_renderer: DefaultSqlExpressionRenderer,
  ) -> None:  # noqa: D
      actual = default_expr_renderer.render_sql_expr(
          SqlAggregateFunctionExpression(
              sql_function=SqlFunction.CONCAT,
              sql_function_args=[
                  SqlColumnReferenceExpression(
                      SqlColumnReference("my_table", "a")
                  ),
                  SqlAggregateFunctionExpression(
                      sql_function=SqlFunction.CONCAT,
                      sql_function_args=[
                          SqlColumnReferenceExpression(
                              SqlColumnReference("my_table", "b")
                          ),
                          SqlColumnReferenceExpression(
                              SqlColumnReference("my_table", "c")
                          ),
                      ],
                  ),
              ],
          )
      ).sql
      assert (
          actual == "CONCAT(my_table.a, CONCAT(my_table.b, my_table.c))"
      )
  
imports: from __future__ import annotations
  import logging
  import textwrap
  import pytest
  from dbt_semantic_interfaces.type_enums.date_part import DatePart
  from dbt_semantic_interfaces.type_enums.time_granularity import TimeGranularity
  from metricflow.sql.render.expr_renderer import DefaultSqlExpressionRenderer
  from metricflow.sql.sql_exprs import SqlAggregateFunctionExpression, SqlBetweenExpression, SqlCastToTimestampExpression, SqlColumnReference, SqlColumnReferenceExpression, SqlColumnReplacements, SqlComparison, SqlComparisonExpression, SqlDateTruncExpression, SqlExtractExpression, SqlFunction, SqlIsNullExpression, SqlLogicalExpression, SqlLogicalOperator, SqlNullExpression, SqlRatioComputationExpression, SqlStringExpression, SqlStringLiteralExpression, SqlWindowFunction, SqlWindowFunctionExpression, SqlWindowOrderByArgument
label_desc: Use image node_id 8 for calling a global function with example usage: test_nested_function_expr(default_expr_renderer) without return types