def METHOD_NAME(self, context: RuleContext) -> LintResult:
    """Nested CASE statement in ELSE clause could be flattened."""
    segment = FunctionalContext(context).segment
    assert segment.select(sp.is_type("case_expression"))
    case1_children = segment.children()
    case1_last_when = case1_children.last(sp.is_type("when_clause")).get()
    case1_else_clause = case1_children.select(sp.is_type("else_clause"))
    case1_else_expressions = case1_else_clause.children(sp.is_type("expression"))
    expression_children = case1_else_expressions.children()
    case2 = expression_children.select(sp.is_type("case_expression"))
    # The len() checks below are for safety, to ensure the CASE inside
    # the ELSE is not part of a larger expression. In that case, it's
    # not safe to simplify in this way -- we'd be deleting other code.
    if (
        not case1_last_when
        or len(case1_else_expressions) > 1
        or len(expression_children) > 1
        or not case2
    ):
        return LintResult()
    # We can assert that this exists because of the previous check.
    assert case1_last_when
    # We can also assert that we'll also have an else clause because
    # otherwise the case2 check above would fail.
    case1_else_clause_seg = case1_else_clause.get()
    assert case1_else_clause_seg
    # Delete stuff between the last "WHEN" clause and the "ELSE" clause.
    case1_to_delete = case1_children.select(
        start_seg=case1_last_when, stop_seg=case1_else_clause_seg
    )
    # Delete the nested "CASE" expression.
    fixes = case1_to_delete.apply(lambda seg: LintFix.delete(seg))
    tab_space_size: int = context.config.get("tab_space_size", ["indentation"])
    indent_unit: str = context.config.get("indent_unit", ["indentation"])
    # Determine the indentation to use when we move the nested "WHEN"
    # and "ELSE" clauses, based on the indentation of case1_last_when.
    # If no whitespace segments found, use default indent.
    indent = (
        case1_children.select(stop_seg=case1_last_when)
        .reversed()
        .select(sp.is_type("whitespace"))
    )
    indent_str = (
        "".join(seg.raw for seg in indent)
        if indent
        else construct_single_indent(indent_unit, tab_space_size)
    )
    # Move the nested "when" and "else" clauses after the last outer
    # "when".
    nested_clauses = case2.children(sp.is_type("when_clause", "else_clause"))
    create_after_last_when = nested_clauses.apply(
        lambda seg: [NewlineSegment(), WhitespaceSegment(indent_str), seg]
    )
    segments = [item for sublist in create_after_last_when for item in sublist]
    fixes.append(LintFix.create_after(case1_last_when, segments, source=segments))
    # Delete the outer "else" clause.
    fixes.append(LintFix.delete(case1_else_clause_seg))
    return LintResult(case2[0], fixes=fixes)