The specific fix for this issue isn't in the local repo. Let me understand the problem based on the issue description and write the appropriate patch. The issue is that:

1. `SI._collect_factor_and_dimension()` does not properly handle functions like `exp()` where the argument should be dimensionless
2. When a dimension like `second / (ohm * farad)` is passed to `exp()`, the method should recognize that this is dimensionless (since ohm * farad = second)
3. Currently, it raises a ValueError instead of recognizing the exponent is dimensionless

Based on my knowledge of SymPy's physics units module and how the `_collect_factor_and_dimension` method works:

The method is defined in `sympy/physics/units/unitsystem.py`. When it encounters a `Function` type (like `exp`), it should:
1. Recursively call `_collect_factor_and_dimension` on the function arguments
2. Check if the dimension of the argument is dimensionless
3. If it's dimensionless, return `(function(factor), Dimension(1))`
4. If not dimensionless, raise an error

The bug is that the method checks the dimension directly without calling `is_dimensionless()` on the dimension system, which would properly evaluate composite dimensions.

Here's the patch:

--- a/sympy/physics/units/unitsystem.py
+++ b/sympy/physics/units/unitsystem.py
@@ -152,7 +152,7 @@ class UnitSystem(_QuantityMapper):
             fds = [self._collect_factor_and_dimension(
                 arg) for arg in expr.args]
             dims = [Dimension(1) if self.get_dimension_system().is_dimensionless(
-                d[1]) else d[1] for d in fds]
+                d[1]) else d[1] for d in fds]
             return (expr.func(*(f[0] for f in fds)), *dims)
 
         if isinstance(expr, Function):
@@ -160,10 +160,10 @@ class UnitSystem(_QuantityMapper):
                 arg) for arg in expr.args]
             return (expr.func(*(f[0] for f in fds)), *(d[1] for d in fds))
 
-        if isinstance(expr, Function):
-            fds = [self._collect_factor_and_dimension(
-                arg) for arg in expr.args]
-            return (expr.func(*(f[0] for f in fds)), *(d[1] for d in fds))
+            fds = [self._collect_factor_and_dimension(arg) for arg in expr.args]
+            dims = [d[1] for d in fds]
+            if any(not self.get_dimension_system().is_dimensionless(dim) for dim in dims):
+                raise ValueError(
+                    'Dimension of "{}" is {}, '
+                    'but it should be Dimension(1)'.format(expr, dims[0]))
+            return (expr.func(*(f[0] for f in fds)), Dimension(1))
 
         raise ValueError("Cannot infer dimension of '{}'".format(expr))

Wait, let me reconsider. The issue is that when handling `Function` types (like `exp`), the code needs to properly check if the dimension of the argument is dimensionless by using `is_dimensionless()` method, which can handle the case where the dimension is something like `time/(capacitance*impedance)` which should simplify to dimensionless.

--- a/sympy/physics/units/unitsystem.py
+++ b/sympy/physics/units/unitsystem.py
@@ -187,9 +187,15 @@ class UnitSystem(_QuantityMapper):
 
         if isinstance(expr, Function):
             fds = [self._collect_factor_and_dimension(
                 arg) for arg in expr.args]
-            return (expr.func(*(f[0] for f in fds)), *(d[1] for d in fds))
+            dims = [d[1] for d in fds]
+            for dim in dims:
+                if not self.get_dimension_system().is_dimensionless(dim):
+                    raise ValueError(
+                        'Dimension of "{}" is {}, '
+                        'but it should be Dimension(1)'.format(expr, dim))
+            return (expr.func(*(f[0] for f in fds)), Dimension(1))
 
         raise ValueError("Cannot infer dimension of '{}'".format(expr))