set sound speed

Hi

i try to set the speed of the sound but it's not working.

```
from brping import Ping1D

# ---------- Configuration ----------
PORT = "/dev/serial0"
BAUDRATE = 115200
SOUND_SPEED_MS = 1447 # à adapter à ton milieu

# -----------------------------------

# Timestamp à l'initialisation
start_time = datetime.now()
FILENAME = f"ping_depth_{start_time.strftime('%Y%m%d_%H%M%S')}.csv"

myPing = Ping1D()
myPing.connect_serial(PORT, BAUDRATE)
rg = myPing.get_profile()
print(f"get_profile: {rg}")

# Conversion en mm/s pour Ping1D
SOUND_SPEED_MM_S = 1450000 # exemple

ok = myPing.set_speed_of_sound(SOUND_SPEED_MM_S)
print(ok)

res = myPing.get_speed_of_sound()
print(res)
```

when i run my code I receive this issue
```
styx4d@Echosondeur:~/Documents $ python Pind1D_only.py
Opening /dev/serial0 at 115200 bps
get_profile: {'distance': 4449, 'confidence': 0, 'transmit_duration': 191, 'ping_number': 45983, 'scan_start': 0, 'scan_length': 6782, 'gain_setting': 6, 'profile_data': b'\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfd\xfdH\x0f,\x90w%\x05\x15@-\x12\x02\x03\x06\x07\t\x06\x02\x01\x02\x00\x00\x01\x03\x04\x01\x00\x01\x00\x00\x00\x00\x01\x01\x00\x00\x03\x06\x06\x01\x01\x00\x00\x00\x00\x00\x01\x05\x03\x00\x00\x00\x00\x01\x00\x00\x00\x01\x01\x00\x00\x01\x04\x00\x00\x00\x01\x02\x00\x02\x01\x00\x00\x00\x00\x03\x06\x08\x07\t\x04\x03\x01\x00\x00\x00\x01\x02\x03\t\n\x10\x0b\x03\x02\x00\x00\x03\x04\x01\x01\x00\x00\x03\x04\x04\x05\x01\x00\x00\x00\x02\x05\x07\x04\x03\x00\x00\x00\x00\x03\x00\x00\x00\x00\x00\x00\x00%\x00\x00\x00\x00\x1f\xffu\x8a\x906\x1e`\x19\x00fF\x17\x00\x1b+\x1f"\x00..~\xed\xfd\x02g\x14\x00(g^P&QN '}
Traceback (most recent call last):
File "/home/styx4d/Documents/Pind1D_only.py", line 26, in
ok = myPing.set_speed_of_sound(SOUND_SPEED_MM_S)
File "/home/styx4d/.local/lib/python3.13/site-packages/bluerobotics_ping-0.2.3-py3.13.egg/brping/ping1d.py", line 520, in set_speed_of_sound
and (self._speed_of_sound != speed_of_sound)):
^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Ping1D' object has no attribute '_speed_of_sound'. Did you mean: 'get_speed_of_sound'?
```

Thanks for your help