Description of the false positive
The lines in question are:

L21 = layout.MultiVector(...)
L12 = layout.MultiVector(...)
K = L21 + L12 + 2.0
beta = K(4)  # Call to a non-callable of builtin-class float.

Where:

• layout.MultiVector returns an instance of MultiVector
• MultiVector.__add__ is overloaded to return an instance of MultiVector
• MultiVector.__call__ is defined

URL to the alert on the project page on LGTM.com

https://lgtm.com/projects/g/pygae/clifford/snapshot/23c8649145cc81a9a44e7b0e445d7e000639101e/files/clifford/tools/g3c/__init__.py#x3c80edcfa911a30d:1