Using python 3.12 generics and mypy

I want to achieve something like this:

from collections import deque
from typing import Iterable

import numpy as np


def mean[T](a: Iterable[T]) -> T:
    s = sum(a)
    return s * (1.0/len(a))


c = mean([1.0, 1.5])
print(c)

a = np.array([1, 2, 3])
b = np.array([4, 5, 6])
c = mean([a, b])
print(c)

print(mean((1,2,3)) )

d = deque([a,b])
print(mean(d))

but I want that code not only correctly work - which is achieved now, but also to be accepted by mypy. As for now I can't overcome errors like this:

mypy mypy_explore.py

    mypy_explore.py:8: error: Argument 1 to "sum" has incompatible type "Iterable[T]"; expected "Iterable[bool]"  [arg-type]
    mypy_explore.py:9: error: Unsupported operand types for / ("float" and "int")  [operator]
    mypy_explore.py:9: error: Argument 1 to "len" has incompatible type "Iterable[T]"; expected "Sized"  [arg-type]
    mypy_explore.py:17: error: Incompatible types in assignment (expression has type "ndarray[Any, dtype[Any]]", variable has type "float")  [assignment]
    Found 4 errors in 1 file (checked 1 source file)

I have tested many methods, also using Protocol, but none of them successfully, I feel that this should be easy to achieve, just a sequence of any type supporting sum and multiplication by number should be accepted, but it is not...

I tried also this:

from collections import deque
from typing import Sequence

import numpy as np


def mean[T](a: Sequence[T]) -> T:
    la = list(a)
    s = a[0]
    for i in la[1:]:
        s = s + i
    return s * (1.0/len(a))


c = mean([1.0, 1.5])
print(c)

a = np.array([1, 2, 3])
b = np.array([4, 5, 6])
c = mean([a, b])
print(c)

print(mean((1,2,3)) )

d = deque([a,b])
print(mean(d))

and errors where like this:

mypy_explore.py : 4 errors 
Unsupported left operand type for + ("T")  [operator] (11:12)
Unsupported operand types for * ("T" and "float")  [operator] (12:11)
Incompatible return value type (got "float", expected "T")  [return-value] (12:11)
Incompatible types in assignment (expression has type "ndarray[Any, dtype[Any]]", variable has type "float")  [assignment] (20:4)