fix: improve schema detection for graph model nodes

[cristipufu]

Development Package

• Add this package as a dependency in your pyproject.toml:

[project]
dependencies = [
  # Exact version:
  "uipath-langchain==0.1.28.dev1003361490",

  # Any version from PR
  "uipath-langchain>=0.1.28.dev1003360000,<0.1.28.dev1003370000"
]

[[tool.uv.index]]
name = "testpypi"
url = "https://test.pypi.org/simple/"
publish-url = "https://test.pypi.org/legacy/"
explicit = true

[tool.uv.sources]
uipath-langchain = { index = "testpypi" }