Describe the bug
If multiple properties use the same $ref, with one of those properties having the same name as the $ref, the generated code fails mypy checks with a [name-defined] error.

To Reproduce

Example schema:
identifier.json:

{
    "$schema": "http://json-schema.org/schema",
    "title": "Identifier",
    "type": "object",
    "properties": {
        "identifier_name": {
            "type": "string"
        }
    }
}

example.json:

{
    "$schema": "http://json-schema.org/schema",
    "title": "Example",
    "type": "object",
    "properties": {
        "identifier": {
            "$ref": "identifier.json"
        },
        "another_identifier": {
            "$ref": "identifier.json"
        }
    }
}

Generated code:
identifier.py:

# generated by datamodel-codegen:
#   filename:  identifier.json
#   timestamp: 2022-09-02T12:22:46+00:00

from __future__ import annotations

from typing import Optional

from pydantic import BaseModel


class Identifier(BaseModel):
    identifier_name: Optional[str] = None

example.py:

# generated by datamodel-codegen:
#   filename:  example.json
#   timestamp: 2022-09-02T12:22:46+00:00

from __future__ import annotations

from typing import Optional

from pydantic import BaseModel

from . import identifier


class Example(BaseModel):
    identifier: Optional[identifier.Identifier] = None
    another_identifier: Optional[identifier.Identifier] = None

Used commandline:

$ datamodel-codegen --input example/ --output example_output/ --field-constraints
$ mypy example_output/ --show-error-codes
example_output/example.py:16: error: Name "identifier.Identifier" is not defined  [name-defined]
Found 1 error in 1 file (checked 3 source files)

Expected behavior
I would expect the generated code to pass mypy checks with no errors. Since the error appears to be caused by the from . import identifier import, changing this to be from . import identifier as identifier_ would work.

Version:

• OS: MacOS
• Python version: 3.8.6
• datamodel-code-generator version: 0.13.1

Additional context
N/A