#### Astronomical Length Scale Conversion

C
```"""
Conversion of length units.
Available Units:
Metre, Kilometre, Megametre, Gigametre,
Terametre, Petametre, Exametre, Zettametre, Yottametre

USAGE :
-> Import this file into their respective project.
-> Use the function length_conversion() for conversion of length units.
-> Parameters :
-> value : The number of from units you want to convert
-> from_type : From which type you want to convert
-> to_type : To which type you want to convert

REFERENCES :
-> Wikipedia reference: https://en.wikipedia.org/wiki/Meter
-> Wikipedia reference: https://en.wikipedia.org/wiki/Kilometer
-> Wikipedia reference: https://en.wikipedia.org/wiki/Orders_of_magnitude_(length)
"""

UNIT_SYMBOL = {
"meter": "m",
"kilometer": "km",
"megametre": "Mm",
"gigametre": "Gm",
"terametre": "Tm",
"petametre": "Pm",
"exametre": "Em",
"zettametre": "Zm",
"yottametre": "Ym",
}
# Exponent of the factor(meter)
METRIC_CONVERSION = {
"m": 0,
"km": 3,
"Mm": 6,
"Gm": 9,
"Tm": 12,
"Pm": 15,
"Em": 18,
"Zm": 21,
"Ym": 24,
}

def length_conversion(value: float, from_type: str, to_type: str) -> float:
"""
Conversion between astronomical length units.

>>> length_conversion(1, "meter", "kilometer")
0.001
>>> length_conversion(1, "meter", "megametre")
1e-06
>>> length_conversion(1, "gigametre", "meter")
1000000000
>>> length_conversion(1, "gigametre", "terametre")
0.001
>>> length_conversion(1, "petametre", "terametre")
1000
>>> length_conversion(1, "petametre", "exametre")
0.001
>>> length_conversion(1, "terametre", "zettametre")
1e-09
>>> length_conversion(1, "yottametre", "zettametre")
1000
>>> length_conversion(4, "wrongUnit", "inch")
Traceback (most recent call last):
...
ValueError: Invalid 'from_type' value: 'wrongUnit'.
Conversion abbreviations are: m, km, Mm, Gm, Tm, Pm, Em, Zm, Ym
"""

from_sanitized = from_type.lower().strip("s")
to_sanitized = to_type.lower().strip("s")

from_sanitized = UNIT_SYMBOL.get(from_sanitized, from_sanitized)
to_sanitized = UNIT_SYMBOL.get(to_sanitized, to_sanitized)

if from_sanitized not in METRIC_CONVERSION:
raise ValueError(
f"Invalid 'from_type' value: {from_type!r}.\n"
f"Conversion abbreviations are: {', '.join(METRIC_CONVERSION)}"
)
if to_sanitized not in METRIC_CONVERSION:
raise ValueError(
f"Invalid 'to_type' value: {to_type!r}.\n"
f"Conversion abbreviations are: {', '.join(METRIC_CONVERSION)}"
)
from_exponent = METRIC_CONVERSION[from_sanitized]
to_exponent = METRIC_CONVERSION[to_sanitized]
exponent = 1

if from_exponent > to_exponent:
exponent = from_exponent - to_exponent
else:
exponent = -(to_exponent - from_exponent)

return value * pow(10, exponent)

if __name__ == "__main__":
from doctest import testmod

testmod()
```