Here we refer to: assert_bytes () from electrum / util.py _lib | 🎩BLACK HAT🎩

Here we refer to:
assert_bytes () from electrum / util.py
_libsecp256k1, SECP256K1_EC_UNCOMPRESSED from electrum / ecc_fast.py (C library for ECDSA signatures and private / public key operations on the secp256k1 curve)
hmac_oneshot () from electrum / crypto.py
Let's borrow them from the corresponding electrum / * py files:
create them in the src directory: util.py, ecc_fast.py, crypto.py, respectively.

And now our init.py will look like this:

__init__.py

from . import ecc
from . import util
from . import ecc_fast
from . import crypto

Then I thought for you and left everything you need from a bunch of unnecessary code:

ecc_fast.py

import os
import sys
import ctypes
from ctypes import (
byref, c_byte, c_int, c_uint, c_char_p, c_size_t, c_void_p, create_string_buffer,
CFUNCTYPE, POINTER, cast
)

SECP256K1_FLAGS_TYPE_MASK = ((1 << 8) - 1)
SECP256K1_FLAGS_TYPE_CONTEXT = (1 << 0)
SECP256K1_FLAGS_TYPE_COMPRESSION = (1 << 1)
# /** The higher bits contain the actual data. Do not use directly. */
SECP256K1_FLAGS_BIT_CONTEXT_VERIFY = (1 << 8)
SECP256K1_FLAGS_BIT_CONTEXT_SIGN = (1 << 9)
SECP256K1_FLAGS_BIT_COMPRESSION = (1 << 8)

# /** Flags to pass to secp256k1_context_create. */
SECP256K1_CONTEXT_VERIFY = (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_VERIFY)
SECP256K1_CONTEXT_SIGN = (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_SIGN)
SECP256K1_CONTEXT_NONE = (SECP256K1_FLAGS_TYPE_CONTEXT)

SECP256K1_EC_COMPRESSED = (SECP256K1_FLAGS_TYPE_COMPRESSION | SECP256K1_FLAGS_BIT_COMPRESSION)
SECP256K1_EC_UNCOMPRESSED = (SECP256K1_FLAGS_TYPE_COMPRESSION)


class LibModuleMissing(Exception): pass


def load_library()

library_paths = ['/usr/lib/libsecp256k1.so.0']

exceptions = []
secp256k1 = None
for libpath in library_paths:
try:
secp256k1 = ctypes.cdll.LoadLibrary(libpath)
except BaseException as e:
exceptions.append(e)
else:
break
if not secp256k1:
print(f'libsecp256k1 library failed to load. exceptions: {repr(exceptions)}')
return None

try:
secp256k1.secp256k1_context_create.argtypes = [c_uint]
secp256k1.secp256k1_context_create.restype = c_void_p

secp256k1.secp256k1_context_randomize.argtypes = [c_void_p, c_char_p]
secp256k1.secp256k1_context_randomize.restype = c_int

secp256k1.secp256k1_ec_pubkey_create.argtypes = [c_void_p, c_void_p, c_char_p]
secp256k1.secp256k1_ec_pubkey_create.restype = c_int

secp256k1.secp256k1_ecdsa_sign.argtypes = [c_void_p, c_char_p, c_char_p, c_char_p, c_void_p, c_void_p]
secp256k1.secp256k1_ecdsa_sign.restype = c_int

secp256k1.secp256k1_ecdsa_verify.argtypes = [c_void_p, c_char_p, c_char_p, c_char_p]
secp256k1.secp256k1_ecdsa_verify.restype = c_int

secp256k1.secp256k1_ec_pubkey_parse.argtypes = [c_void_p, c_char_p, c_char_p, c_size_t]
secp256k1.secp256k1_ec_pubkey_parse.restype = c_int

secp256k1.secp256k1_ec_pubkey_serialize.argtypes = [c_void_p, c_char_p, c_void_p, c_char_p, c_uint]
secp256k1.secp256k1_ec_pubkey_serialize.restype = c_int

secp256k1.secp256k1_ecdsa_signature_parse_compact.argtypes = [c_void_p, c_char_p, c_char_p]
secp256k1.secp256k1_ecdsa_signature_parse_compact.restype = c_int

secp256k1.secp256k1_ecdsa_signature_normalize.argtypes = [c_void_p, c_char_p, c_char_p]
secp256k1.secp256k1_ecdsa_signature_normalize.restype = c_int

secp256k1.secp256k1_ecdsa_signature_serialize_compact.argtypes = [c_void_p, c_char_p, c_char_p]
secp256k1.secp256k1_ecdsa_signature_serialize_compact.restype = c_int

secp256k1.secp256k1_ecdsa_signature_parse_der.argtypes = [c_void_p, c_char_p, c_char_p, c_size_t]
secp256k1.secp256k1_ecdsa_signature_parse_der.restype = c_int

secp256k1.secp256k1_ecdsa_signature_serialize_der.argtypes = [c_void_p, c_char_p, c_void_p, c_char_p]
secp256k1.secp256k1_ecdsa_signature_serialize_der.restype = c_int