In Python, I want to add a new function that receive this sql string, and format it based on indentation rules, so this formatting should be related to the indentation of the variables. At most, a select or any other methods should have. I tried using sqlparse library but I think we need a custom formatted for this complex task.

The rules for the indentation are like this:

1. Queries may consist of one or more lines and SQL statements must be separated by a blank line.
2. Each nesting level must have three spaces, do not use tabs.
3. Items of a similar nature should be placed in the same column.

Example of correct indented sql strings:

```sql
exec @w_error = sp_something
   @i_var1            = @w_var1                ,
   @i_longer_var2     = @w_longer_var2         ,
   @i_var3            = @w_var3                ,
   @o_var_out1        = @w_var_out1        out ,
   @o_var_longer_out2 = @w_var_longer_out2 out
```

Another example, this time in a select:
```sql
select
@w_var1             = var1,
@w_some_var2        = op_estado,
@w_some_longer_var3 = op_migrada,
@w_var4             = var4,
from some_table
where some_var = @w_some_var
```

As you can see, they are aligned not only by the "=", but also by "out" keyword and the commas. The comma code I already have a different method, so you can focus on the "=" and the "out" part.

4. This often happens in INSERT queries: if necessary, use three columns in both the field area and the data area aligned one space after the longest column name, the nesting levels between the first and second part of an insert are independent.

Example of correct indented sql strings:
```sql
insert into some_table (
some_Var1,         some_Var2,   some_longer_var3,
another_long_var4, some_var5,   another_var6,
small_var7,        maybe_a_var8)
values (
@i_some_Var1, @w_some_Var2, @i_some_longer_var3,
@w_something, @w_some,      @w_thing,
'N',          0)


Here is my current code, it is working correctly up to the part of getting an unrelated "=" wrong here:

   select @w_error= @w_return

and the code should output this (missing an space before the =):

   select @w_error = @w_return

Here is my current working code:

def format_sql(sql):
    lines = sql.split('\n')
    formatted_lines = []
    current_block = []

    def format_block(block):
        max_length_before_equals = max(len(line.split('=')[0].strip()) for line in block if '=' in line)
        formatted_block = []
        for line in block:
            if '=' in line:
                parts = line.split('=')
                left_part = parts[0].rstrip().ljust(max_length_before_equals + 1)
                right_part = '= ' + parts[1].strip()
                formatted_block.append(left_part + right_part)
            else:
                formatted_block.append(line)
        return formatted_block

    for line in lines:
        stripped_line = line.strip()

        # Handle blank lines
        if not stripped_line:
            if current_block:
                formatted_lines.extend(format_block(current_block))
                current_block = []
            formatted_lines.append('')
            continue

        # Handle blocks with '=' or 'out'
        if '=' in stripped_line or 'out' in stripped_line:
            current_block.append(line)
        else:
            if current_block:
                formatted_lines.extend(format_block(current_block))
                current_block = []
            formatted_lines.append(line)

    # Handle the last block if it exists
    if current_block:
        formatted_lines.extend(format_block(current_block))

    # Ensure no space between '!' and '='
    for i, line in enumerate(formatted_lines):
        if '! =' in line:
            formatted_lines[i] = line.replace('! =', '!=')

    return '\n'.join(formatted_lines)

```sql
exec @placeholder1 = p_placeholder2
@placeholder3 = @placeholder3,
@placeholder4    = @placeholder4,
@placeholder5       = @placeholder5,
@placeholder6 = @placeholder6,
@placeholder7    = @placeholder7,
@placeholder8      = @placeholder8,
@placeholder9       = @placeholder9,
@placeholder10         = @placeholder10,
@placeholder11   = @placeholder11,
@placeholder12  = @placeholder12,
@placeholder13       = @placeholder13,
@placeholder14   = @placeholder14,
@placeholder15       = @placeholder15,
@placeholder16        = @placeholder16,
@placeholder17   = @placeholder17

if @placeholder1 != 0
begin --ES ERROR
   select @placeholder18 = @placeholder1
   goto ERROR
end --ES ERROR

select @placeholder19 = 0

select @placeholder20 = sum(placeholder21)
from  placeholder22
where placeholder23  = @placeholder13
and   placeholder24 = @placeholder5
and   placeholder25         = @placeholder4
and   placeholder26  = 'I'
and   placeholder27 = 'P'
```

formatted_query = format_sql(query)
print(formatted_query)